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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.
11

Various Approaches on Parameter Estimation in Mixture and Non-Mixture Cure Models

Unknown Date (has links)
Analyzing life-time data with long-term survivors is an important topic in medical application. Cure models are usually used to analyze survival data with the proportion of cure subjects or long-term survivors. In order to include the propor- tion of cure subjects, mixture and non-mixture cure models are considered. In this dissertation, we utilize both maximum likelihood and Bayesian methods to estimate model parameters. Simulation studies are carried out to verify the nite sample per- formance of the estimation methods. Real data analyses are reported to illustrate the goodness-of- t via Fr echet, Weibull and Exponentiated Exponential susceptible distributions. Among the three parametric susceptible distributions, Fr echet is the most promising. Next, we extend the non-mixture cure model to include a change point in a covariate for right censored data. The smoothed likelihood approach is used to address the problem of a log-likelihood function which is not di erentiable with respect to the change point. The simulation study is based on the non-mixture change point cure model with an exponential distribution for the susceptible subjects. The simulation results revealed a convincing performance of the proposed method of estimation. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection
12

The Study of Lifetime Prediction and Reliability Test of Co-Chromaticity Glass and Silicone Phosphor

Liou, Jyun-Sian 04 August 2011 (has links)
A Ce:YAG-doped glass phosphor layer instead of conventional Ce:YAG-doped silicone phosphor layer as phosphor-converted white-light emitting diodes (PC-WLEDs) is demonstrated. The advantage of employing doped glass encapsulation in high power PC-WLEDs could be explained the material property of glass transition temperature of 750¢J was higher than silicone of 150¢J. The lumen degradation, chromaticity shift, color temperature change, transmittance, and fluorescence spectrum in glass and silicone based high-power PC-WLEDs under thermal aging at 150¢J, 200¢J, and 250¢J is compared and presented. Under highest temperature of 250¢J, the glass and silicone encapsulation base d PC-WLEDs exhibited 8.15% and 38.85% in lumen loss, 1.07 and 7.32 in chromaticity shift, 856 K and 3666 K in color temperature change, 4.21% and 28.1% in transmittance loss, respectively. However, the excitation spectrum altered as slight as emission spectrum before and after experiments. After aging test, the mean-time-to-failure (MTTF) evaluation of glass and silicone encapsulation materials for PC-WLEDs in accelerated thermal tests is also compared and presented by the using of Weibull distribution and Arrhenius equation. The MTTF of PC-WLEDs is defined the lumen decayed to 90%. The results showed that the glass as encapsulation material of PC-WLEDs exhibited higher MTTF than the silicone encapsulation by about 4.81, 5.92, and 7.53 times in lumen loss at 150¢J, 200¢J, and 250¢J, respectively. The results of the lumen loss, chromaticity shift, and MTTF investigations demonstrated that the thermal-stability performance of the glass based PC-WLEDs were better than silicone based PC-WLEDs at 150¢J, 200¢J, and 250¢J. A better thermal stability phosphor layer of glass as encapsulation material may be beneficial to the many applications where the LED modules with high power and high reliability are demanded.
13

Model selection criteria based on Kullback information measures for Weibull, logistic, and nonlinear regression frameworks /

Kim, Hyun-Joo, January 2000 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 104-107). Also available on the Internet.
14

Model selection criteria based on Kullback information measures for Weibull, logistic, and nonlinear regression frameworks

Kim, Hyun-Joo, January 2000 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 104-107). Also available on the Internet.
15

Weibull parameter estimation using genetic algorithms and a heuristic approach to cut-set analysis

Thomas, Gina M. January 1995 (has links)
Thesis (M.S.)--Ohio University, March, 1995. / Title from PDF t.p.
16

Weibull analysis of loading rate effect on the toughening mechanisms of ABS

Xu, Jie. January 2009 (has links)
Thesis (M. Sc.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on August 7, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Mechanical Engineering, University of Alberta." Includes bibliographical references.
17

Comparison of k-Weibull populations under random censoring /

Abeyratne, Anura T. January 1996 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 125-127). Also available on the Internet.
18

Comparison of k-Weibull populations under random censoring

Abeyratne, Anura T. January 1996 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 125-127). Also available on the Internet.
19

Inferring congestion from delay and loss characteristics using parameters of the three-parameter Weibull distribution

Ramaisa, Motlalepula. January 2005 (has links)
Thesis (M.Sc.)(Applied sciences)--University of Pretoria, 2005. / Includes bibliographical references. Available on the Internet via the World Wide Web.
20

Δημιουργία αρχείου ανεμολογικών δεδομένων και ανάπτυξη προγράμματος υπολογισμού καμπυλών Weibull για τη διαχείριση της αιολικής ενέργειας

Γκίκας, Δημήτριος 14 February 2012 (has links)
Η παρούσα διπλωματική εργασία αφορά την διαχείριση της αιολικής ενέργειας και την δημιουργία προγράμματος υπολογισμού των καμπυλών «Weibull» σε μετρημένα ανεμολογικά στοιχεία περιοχών, και δυνατότητα αποθήκευσης, επεξεργασίας και ανάκτησης δεδομένων ανά περιοχή. Αρχικά στο πρώτο κεφάλαιο μελετώνται μερικές θεμελιώδης αρχές που διέπουν τον άνεμο όπως για παράδειγμα η ισχύς του. Στην συνέχεια αναλύεται η μεταβλητότητα των ανέμων με τον χρόνο, τον χώρο και την ύπαρξη επιφανειακών εμποδίων αλλά και η εξάρτηση του από το ύψος. Στο δεύτερο κεφάλαιο γίνεται μια ιστορική αναδρομή στην ανάπτυξη της αιολικής ενέργειας αλλά και προβλέψεις για τις μελλοντικές εξελίξεις της. Στο κομμάτι αυτό παρουσιάζεται και η ανάπτυξη της αιολικής ενέργειας στην Ελλάδα. Αναλύονται επίσης ζητήματα που αφορούν την παραγωγή ενέργειας, το κόστος παραγωγής, το κόστος αιολικής ενέργειας, την διασύνδεση στο δίκτυο παροχής αλλά και περιβαλλοντολογικά ζητήματα. Στο τρίτο κεφάλαιο ταξινομούνται οι ανεμογεννήτριες με βάση κάποια κύρια χαρακτηριστικά τους, αναλύονται τα μέρη ανεμογεννήτριας οριζοντίου άξονα και περιγράφονται οι σχεδιαστικές επιλογές για τα κύρια μέρη. Το τέταρτο κεφάλαιο αφορά τα χαρακτηριστικά της αιολικής απόδοσης. Συγκεκριμένα περιγράφονται έννοιες όπως αυτή της αιολικής διείσδυσης ενός αιολικού πάρκου ή του συντελεστή δυναμικού της γεννήτριας, εκτιμάται η ετήσια ενεργειακή παραγωγή, και αναφέρεται η αξιοπιστία των αιολικών συστημάτων (διαθεσιμότητα, ανταποδοτικότητα κόστους κλπ). Στο κεφάλαιο πέντε, αναλύεται η διανομή Weibull : μιας συνεχής κατανομή πιθανότητας, η οποία προσδιορίζει την πιθανότητα εμφάνισης όλως των δυνατών ταχυτήτων ανέμου σε μια περιοχή βάση μόνο δύο παραμέτρων. Οι παράμετροι αυτοί υπολογίζονται. Τέλος στο κεφάλαιο έξι επεξηγείται η λειτουργία του προγράμματος μας και εφαρμόζεται ένα παράδειγμα με μετρημένα ανεμολογικά στοιχεία της περιοχής «Χώρα Κύθνου» για το έτος 1984. / This thesis has to do with the management of wind energy and the construction of a java program for calculating the “Weibull” curves on measured wind data of areas, giving the capability of storage, editing and retrieving the data of each area. To begin with, in the first chapter some fundamental principles of wind, such as its power, are studied. Later on, we study the variability of wind in relation with the time, location and the existence of obstacles and the dependence of the wind on height. In the second chapter, we examine the history of the early development of wind energy and forecasts for future developments. In this part, we also examine the development of wind energy in Greece. Moreover, we describe issues related to energy production, wind energy costs, generation costs, connection on the grid and environmental issues as well. In third chapter, wind turbines are sorted in relation to some basic characteristics, then the basic parts of horizontal axis wind turbines are described and later on we state design choices of the main parts. The fourth chapter has to do with the characteristics of wind energy performance. To be more accurate, we estimate the annual energy production and we indicate the reliability of wind energy systems (like availability and so on). We also introduce the terms of capacity factor of the generator. In chapter five, we analyze the Weibull distribution : a continuous probability distribution, which determines the probability of all the wind speeds appearance in an area based on only two parameters. These parameters are calculated. Finally, in the sixth chapter, the operation of the java program is explained and an example with measured wind data of the area «Χώρα Κύθνου» for the year 1984 is applied.

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