Dissertations / Theses on the topic 'Topic model methods'
To see the other types of publications on this topic, follow the link: Topic model methods.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 23 dissertations / theses for your research on the topic 'Topic model methods.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
王詠媚 and Wing-mei Wong. "Some topics in model selection in financial time series analysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31225366.
Full text
2
Forster, Jeri E. "Varying-coefficient models for longitudinal data : piecewise-continuous, flexible, mixed-effects models and methods for analyzing data with nonignorable dropout /." Connect to full text via ProQuest. Limited to UCD Anschutz Medical Campus, 2006.
Find full textAbstract:
Thesis (Ph.D. in Biostatistics) -- University of Colorado at Denver and Health Sciences Center, 2006.Typescript. Includes bibliographical references (leaves 72-75). Free to UCD Anschutz Medical Campus. Online version available via ProQuest Digital Dissertations;
3
McCarthy, Shane A. "Topics in nonlinear self-dual supersymmetric theories." University of Western Australia. School of Physics, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0045.
Full textAbstract:
[Truncated abstract. Formulae and special characters can only be approximated. See PDF version for accurate reproduction.] Theories of self-dual supersymmetric nonlinear electrodynamics are generalized to a curved superspace of 4D N = 1 supergravity, for both the old-minimal and the newminimal versions of N = 1 supergravity. We derive the self-duality equation, which has to be satisfied by the action functional of any U(1) duality invariant model of a massless vector multiplet, and show that such models are invariant under a superfield Legendre transformation. We construct a family of self-dual nonlinear models, which includes a minimal curved superspace extension of the N = 1 supersymmetric Born- Infeld action. The supercurrent and supertrace of such models are explicitly derived and proved to be duality invariant. The requirement of nonlinear self-duality turns out to yield nontrivial couplings of the vector multiplet to Kähler sigma models. We explicitly construct such couplings in the case when the matter chiral multiplets are inert under the duality rotations, and more specifically to the dilaton-axion chiral multiplet when the group of duality rotations is enhanced to SL(2,R). The component structure of the nonlinear dynamical systems introduced proves to be more complicated, especially in the presence of supergravity, as compared with well-studied effective supersymmetric theories containing at most two derivatives (including nonlinear Kähler sigma-models). As a result, when deriving their canonically normalized component actions, the traditional approach becomes impractical and cumbersome. We find it more efficient to follow the Kugo-Uehara scheme which consists of (i) extending the superfield theory to a super-Weyl invariant system; and then (ii) applying a plain component reduction along with imposing a suitable super-Weyl gauge condition. This scheme is implemented in order to derive the bosonic action of the SL(2,R) duality invariant coupling to the dilaton-axion chiral multiplet and a Kähler sigma-model.
4
Syrén, Ludvig. "A method for introducing flexibility in rigid multibodies from reduced order elastic models." Thesis, Umeå universitet, Institutionen för fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-160417.
Full textAbstract:
In multibody dynamics simulation of robots and vehicles it is common to model the systems as being composed of mainly rigid bodies with articulation joints. With the trend to more lightweight robots, however, the structural flexibility of the robots link’s needs to be considered for realistic dynamic simulations. The link’s geometries are complex and finite element models (FEM) are required to compute the deformations. However, FEM includes too many degrees of freedom for time-efficient dynamics simulation. A popular method is to generate reduced order models from the FE models, but with much fewer degrees of freedom, for fast and precise simulations. In this thesis a method for introducing reduced order models in rigid multibody systems was developed. The method is to divide a rigid body into two rigid bodies. Their relative movement is described by a six degree of freedom restoration force, determined with a reduced order model from Guyan reduction (static condensation). The method was validated for quasistatic deformation of a homogenous beam, a robot link arm with a more complex geometry and in multibody dynamics simulations. Finally the method was tested in simulation of a complete ABB robot with joint actuators, and any significant differences in the motion of the robot tool centre point due to replacing a rigid link arm by a flexible one was demonstrated.The method show good results for computing deformations of the homogenous beam, of the link arm and in the multibody simulation. The differences observed in simulation of a complete robot was expected and demonstrated the method to be applicable in robotic simulations.
5
Wagner, Brandie D. "Permutation based microarray gene selection methods with covarience adjustment applicable to complex diseases /." Connect to full text via ProQuest. Limited to UCD Anschutz Medical Campus, 2007.
Find full textAbstract:
Thesis (Ph.D. in Analytic Health Sciences) -- University of Colorado Denver, 2007.Typescript. Includes bibliographical references (leaves 57-60). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;
6
Cohen, Margaret A. "Estimating the growth rate of harmful algal blooms using a model averaged method." View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-1/rp/cohenm/margaretcohen.pdf.
Full text
7
Kronberg, Simon. "Morphology Formation from Ternary Mixtures upon Evaporation : a Square Cell Model Approach." Thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik (from 2013), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-72624.
Full textAbstract:
We present a novel modelling approach for the morphology formation from ternary mixtures upon evaporation, which takes into consideration two different length scales of the interaction, and further allows for these length scales to be altered. A quantitative study of the interfacial energy hints towards the existence of a mesoscopic regime - further research is needed to verify the validity of this claim however. We also demonstrate that the solvent initially follows a Fickian law of diffusion, then deviates from this behaviour, presumably due to the phase separated regions produced by the two remaining (active) components. We also attempt to bridge the gap between this work and a hypothetical three-dimensional model by considering a top-down view of the system. Here, we observe domain growth dominated by Ostwald ripening, with some coalescence. The domain growth was further characterised using Fourier image analysis.Vi presenterar en ny modellansats för morfologiformation från trekomponentsblandningar under avdunstning, som tar hänsyn till två olika längdskalor hos interaktionen, samt möjliggör förändring av dessa längdskalor. En kvantitativ studie av energin vid domängränserna tyder på att det finns en mesoskopisk regim - ytterligare forskning är dock nödvändig för att verifiera giltigheten av detta påstående. Vi visar också att lösningsmedlet ursprungligen följer en Fickiansk diffusionslag, för att senare avvika från detta beteende, förmodligen på grund av de tydliga domänerna som produceras av de två återstående (aktiva) komponenterna. Vi försöker också minska klyftan mellan det här arbetet och en hypotetisk tredimensionell modell genom att behandla systemet uppifrån. Här observerar vi domäntillväxt dominerad av 'Ostwald ripening', med viss koalescens. Domäntillväxten karakteriserades vidare med hjälp av Fourier-bildanalys.
8
Podosinnikova, Anastasia. "Sur la méthode des moments pour l'estimation des modèles à variables latentes." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE050/document.
Full textAbstract:
Les modèles linéaires latents sont des modèles statistique puissants pour extraire la structure latente utile à partir de données non structurées par ailleurs. Ces modèles sont utiles dans de nombreuses applications telles que le traitement automatique du langage naturel et la vision artificielle. Pourtant, l'estimation et l'inférence sont souvent impossibles en temps polynomial pour de nombreux modèles linéaires latents et on doit utiliser des méthodes approximatives pour lesquelles il est difficile de récupérer les paramètres. Plusieurs approches, introduites récemment, utilisent la méthode des moments. Elles permettent de retrouver les paramètres dans le cadre idéalisé d'un échantillon de données infini tiré selon certains modèles, mais ils viennent souvent avec des garanties théoriques dans les cas où ce n'est pas exactement satisfait. Dans cette thèse, nous nous concentrons sur les méthodes d'estimation fondées sur l'appariement de moment pour différents modèles linéaires latents. L'utilisation d'un lien étroit avec l'analyse en composantes indépendantes, qui est un outil bien étudié par la communauté du traitement du signal, nous présentons plusieurs modèles semiparamétriques pour la modélisation thématique et dans un contexte multi-vues. Nous présentons des méthodes à base de moment ainsi que des algorithmes pour l'estimation dans ces modèles, et nous prouvons pour ces méthodes des résultats de complexité améliorée par rapport aux méthodes existantes. Nous donnons également des garanties d'identifiabilité, contrairement à d'autres modèles actuels. C'est une propriété importante pour assurer leur interprétabilitéLatent linear models are powerful probabilistic tools for extracting useful latent structure from otherwise unstructured data and have proved useful in numerous applications such as natural language processing and computer vision. However, the estimation and inference are often intractable for many latent linear models and one has to make use of approximate methods often with no recovery guarantees. An alternative approach, which has been popular lately, are methods based on the method of moments. These methods often have guarantees of exact recovery in the idealized setting of an infinite data sample and well specified models, but they also often come with theoretical guarantees in cases where this is not exactly satisfied. In this thesis, we focus on moment matchingbased estimation methods for different latent linear models. Using a close connection with independent component analysis, which is a well studied tool from the signal processing literature, we introduce several semiparametric models in the topic modeling context and for multi-view models and develop moment matching-based methods for the estimation in these models. These methods come with improved sample complexity results compared to the previously proposed methods. The models are supplemented with the identifiability guarantees, which is a necessary property to ensure their interpretability. This is opposed to some other widely used models, which are unidentifiable
9
Kim, Kwangmoo. "Topics in the theory of inhomogeneous media composite superconductors and dielectrics /." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180537980.
Full text
10
Das, Manirupa. "Neural Methods Towards Concept Discovery from Text via Knowledge Transfer." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1572387318988274.
Full text
11
Wiberg, Viktor. "Terrain machine learning : A predictive method for estimating terrain model parameters using simulated sensors, vehicle and terrain." Thesis, Umeå universitet, Institutionen för fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-149815.
Full textAbstract:
Predicting terrain trafficability of deformable terrain is a difficult task with applications in e.g, forestry, agriculture, exploratory missions. The currently used techniques are neither practical, efficient, nor sufficiently accurate and inadequate for certain soil types. An online method which predicts terrain trafficability is of interest for any vehicle with purpose to reduce ground damage, improve steering and increase mobility. This thesis presents a novel approach for predicting the model parameters used in modelling a virtual terrain. The model parameters include particle stiffness, tangential friction, rolling resistance and two parameters related to particle plasticity and adhesion. Using multi-body dynamics, both vehicle and terrain can be simulated, which allows for an efficient exploration of a great variety of terrains. A vehicle with access to certain sensors can frequently gather sensor data providing information regarding vehicle-terrain interaction. The proposed method develops a statistical model which uses the sensor data in predicting the terrain model parameters. However, these parameters are specified at model particle level and do not directly explain bulk properties measurable on a real terrain. Simulations were carried out of a single tracked bogie constrained to move in one direction when traversing flat, homogeneous terrains. The statistical model with best prediction accuracy was ridge regression using polynomial features and interaction terms of second degree. The model proved capable of predicting particle stiffness, tangential friction and particle plasticity, with moderate accuracy. However, it was deduced that the current predictors and training scenarios were insufficient in estimating particle adhesion and rolling resistance. Nevertheless, this thesis indicates that it should be possible to develop a method which successfully predicts terrain model properties.
12
"Bootstrap distribution for testing a change in the cox proportional hazard model." 2000. http://library.cuhk.edu.hk/record=b5890302.
Full textAbstract:
Lam Yuk Fai.Thesis (M.Phil.)--Chinese University of Hong Kong, 2000.
Includes bibliographical references (leaves 41-43).
Abstracts in English and Chinese.
Chapter 1 --- Basic Concepts --- p.9
Chapter 1.1 --- Survival data --- p.9
Chapter 1.1.1 --- An example --- p.9
Chapter 1.2 --- Some important functions --- p.11
Chapter 1.2.1 --- Survival function --- p.12
Chapter 1.2.2 --- Hazard function --- p.12
Chapter 1.3 --- Cox Proportional Hazards Model --- p.13
Chapter 1.3.1 --- A special case --- p.14
Chapter 1.3.2 --- An example (continued) --- p.15
Chapter 1.4 --- Extension of the Cox Proportional Hazards Model --- p.16
Chapter 1.5 --- Bootstrap --- p.17
Chapter 2 --- A New Method --- p.19
Chapter 2.1 --- Introduction --- p.19
Chapter 2.2 --- Definition of the test --- p.20
Chapter 2.2.1 --- Our test statistic --- p.20
Chapter 2.2.2 --- The alternative test statistic I --- p.22
Chapter 2.2.3 --- The alternative test statistic II --- p.23
Chapter 2.3 --- Variations of the test --- p.24
Chapter 2.3.1 --- Restricted test --- p.24
Chapter 2.3.2 --- Adjusting for other covariates --- p.26
Chapter 2.4 --- Apply with bootstrap --- p.28
Chapter 2.5 --- Examples --- p.29
Chapter 2.5.1 --- Male mice data --- p.34
Chapter 2.5.2 --- Stanford heart transplant data --- p.34
Chapter 2.5.3 --- CGD data --- p.34
Chapter 3 --- Large Sample Properties and Discussions --- p.35
Chapter 3.1 --- Large sample properties and relationship to goodness of fit test --- p.35
Chapter 3.1.1 --- Large sample properties of A and Ap --- p.35
Chapter 3.1.2 --- Large sample properties of Ac and A --- p.36
Chapter 3.2 --- Discussions --- p.37
13
"Analysis of health-related quality of life data in clinical trial with non-ignorable missing based on pattern mixture model." Thesis, 2006. http://library.cuhk.edu.hk/record=b6074225.
Full textAbstract:
Conclusion. The missing data is a common problem in clinical trial. The methodology development is urgently needed to detect the difference of two treatments drug in patient quality of life. The modified pattern mixture model incorporating generalized estimating equation method or multiple imputation method provides a solution to tackle the non-ignorable missing data problem. Different clinical trials with various treatment schedules, missing data patterns will be formed. Further studies are needed to study the optimal choice of patterns under the methods.Introduction. Health-related Quality of Life (HRQoL) has now been included as a major endpoint in many cancer clinical trials in addition to the traditional endpoints such as tumor response and survival. It refers to how illness or its treatment affects patients' ability to function and whether it induces symptoms. Toxicity, progression and death are common outcome affecting patient's QOL in cancer trial. Since this type of missing data are not occurred at random and are called non-ignorable missing data, conventional methods of analyses are not appropriate. It is important to develop general methods to deal with this problem so that treatment effectiveness for improving patient's QOL or those with serious side effect that is detrimental to patient's QOL can be identified.
Methods. The generalized estimating equation based on modified pattern mixture model is constructed to deal with non-ignorable missing data problem. We conducted a simulation study to examine performance of the model for different types of data. Two scenarios were examined. The first case assumes that two groups have quadratic trend but with different rates of change. The second case assumes that one group has linear trend with time while the other group has quadratic trend with time. Moreover, the second methodology is the multiple imputation based on modified pattern mixture model. The main idea is to resample the data within each pattern to create the full data set and use the standard method to analyze the data. Comparison between two methods was carried out in this study.
Recently, joint models for the QOL outcomes and the indicators of drop-outs are used in longitudinal studies to correct for non-ignorable missing. Two broad classes of joint models, selection model and pattern mixture model, were used. Most of the methodology has been developed in the selection model while the pattern mixture model has attracted less attention due to the identifiability problem. Although pattern mixture model has its own limitation, a modified version of this model incorporating Generalized Estimating Equation can be used in practice.
Result. The power of generalized estimating equation alone is higher than pattern mixture model when the missing data is missing at random. Moreover, the bias of generalized estimating equation is less than that of pattern mixture model when the missing data is missing at random. However, the pattern mixture model performs well when the missing data is missing not at random. On the other hand, the modified pattern mixture model has higher power than the standard pattern mixture model if one group has quadratic trend and other group has linear trend. However, the power of modified pattern mixture model is similar or worst than the standard when the data is both quadratic trends with different rates of change. On the other hand, the results of multiple imputation based on modified pattern mixture model were similar but the power was less than the generalized estimating equation model.
Mo Kwok Fai.
"August 2006."
Adviser: Benny Zee.
Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 6051.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references (p. 91-93).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.
14
Du, Lan. "Non-parametric bayesian methods for structured topic models." Phd thesis, 2011. http://hdl.handle.net/1885/149800.
Full textAbstract:
The proliferation of large electronic document archives requires new techniques for automatically analysing large collections, which has posed several new and interesting research challenges. Topic modelling, as a promising statistical technique, has gained significant momentum in recent years in information retrieval, sentiment analysis, images processing, etc. Besides existing topic models, the field of topic modelling still needs to be further explored using more powerful tools. One potentially useful area is to directly consider the document structure ranging from semantically high-level segments (e.g., chapters, sections, or paragraphs) to low-level segments (e.g., sentences or words) in topic modeling. This thesis introduces a family of structured topic models for statistically modeling text documents together with their intrinsic document structures. These models take advantage of non-parametric Bayesian techniques (e.g., the two-parameter Poisson-Dirichlet process (PDP)) and Markov chain Monte Carlo methods. Two preliminary contributions of this thesis are 1. The Compound Poisson-Dirichlet process (CPDP): it is an extension of the PDP that can be applied to multiple input distributions. 2. Two Gibbs sampling algorithms for the PDP in a finite state space: these two samplers are based on the Chinese restaurant process that provides an elegant analogy of incremental sampling for the PDP. The first, a two-stage Gibbs sampler, arises from a table multiplicity representation for the PDP. The second is built on top of a table indicator representation. In a simply controlled environment of multinomial sampling, the two new samplers have fast convergence speed. These support the major contribution of this thesis, which is a set of structured topic models: Segmented Topic Model (STM) which models a simple document structure with a four-level hierarchy by mapping the document layout to a hierarchical subject structure. It performs significantly better than the latent Dirichlet allocation model and other segmented models at predicting unseen words. Sequential Latent Dirichlet Allocation (SeqLDA) which is motivated by topical correlations among adjacent segments (i.e., the sequential document structure). This new model uses the PDP and a simple first-order Markov chain to link a set of LDAs together. It provides a novel approach for exploring the topic evolution within each individual document. Adaptive Topic Model (AdaTM) which embeds the CPDP in a simple directed acyclic graph to jointly model both hierarchical and sequential document structures. This new model demonstrates in terms of per-word predictive accuracy and topic distribution profile analysis that it is beneficial to consider both forms of structures in topic modelling. - provided by Candidate.
15
Deshwar, Amit Gulab. "Tumor Gene Expression Purification Using Infinite Mixture Topic Models." Thesis, 2013. http://hdl.handle.net/1807/35597.
Full textAbstract:
There is significant interest in using gene expression measurements to aid in the personalization of medical treatment. The presence of significant normal tissue contamination in tumor samples makes it difficult to use tumor expression measurements to predict clinical variables and treatment response. I present a probabilistic method, TMMpure, to infer the expression profile of the cancerous tissue using a modified topic model that contains a hierarchical Dirichlet process prior on the cancer profiles. I demonstrate that TMMpure is able to infer the expression profile of cancerous tissue and improves the power of predictive models for clinical variables using expression profiles.
16
Darling, William Michael. "Generalized Probabilistic Topic and Syntax Models for Natural Language Processing." Thesis, 2012. http://hdl.handle.net/10214/4001.
Full textAbstract:
This thesis proposes a generalized probabilistic approach to modelling document collections along the combined axes of both semantics and syntax. Probabilistic topic (or semantic) models view documents as random mixtures of unobserved latent topics which are themselves represented as probabilistic distributions over words. They have grown immensely in popularity since the introduction of the original topic model, Latent Dirichlet Allocation (LDA), in 2004, and have seen successes in computational linguistics, bioinformatics, political science, and many other fields. Furthermore, the modular nature of topic models allows them to be extended and adapted to specific tasks with relative ease. Despite the recorded successes, however, there remains a gap in combining axes of information from different sources and in developing models that are as useful as possible for specific applications, particularly in Natural Language Processing (NLP). The main contributions of this thesis are two-fold. First, we present generalized probabilistic models (both parametric and nonparametric) that are semantically and syntactically coherent and contain many simpler probabilistic models as special cases. Our models are consistent along both axes of word information in that an LDA-like component sorts words that are semantically related into distinct topics and a Hidden Markov Model (HMM)-like component determines the syntactic parts-of-speech of words so that we can group words that are both semantically and syntactically affiliated in an unsupervised manner, leading to such groups as verbs about health care and nouns about sports. Second, we apply our generalized probabilistic models to two NLP tasks. Specifically, we present new approaches to automatic text summarization and unsupervised part-of-speech (POS) tagging using our models and report results commensurate with the state-of-the-art in these two sub-fields. Our successes demonstrate the general applicability of our modelling techniques to important areas in computational linguistics and NLP.
17
Akhil, P. T. "Topics in Network Utility Maximization : Interior Point and Finite-step Methods." Thesis, 2017. http://hdl.handle.net/2005/3268.
Full textAbstract:
Network utility maximization has emerged as a powerful tool in studying flow control, resource allocation and other cross-layer optimization problems. In this work, we study a flow control problem in the optimization framework. The objective is to maximize the sum utility of the users subject to the flow constraints of the network. The utility maximization is solved in a distributed setting; the network operator does not know the user utility functions and the users know neither the rate choices of other users nor the flow constraints of the network.
We build upon a popular decomposition technique proposed by Kelly [Eur. Trans. Telecommun., 8(1), 1997] to solve the utility maximization problem in the aforementioned distributed setting. The technique decomposes the utility maximization problem into a user problem, solved by each user and a network problem solved by the network. We propose an iterative algorithm based on this decomposition technique. In each iteration, the users communicate to the network their willingness to pay for the network resources. The network allocates rates in a proportionally fair manner based on the prices communicated by the users. The new feature of the proposed algorithm is that the rates allocated by the network remains feasible at all times. We show that the iterates put out by the algorithm asymptotically tracks a differential inclusion. We also show that the solution to the differential inclusion converges to the system optimal point via Lyapunov theory. We use a popular benchmark algorithm due to Kelly et al. [J. of the Oper. Res. Soc., 49(3), 1998] that involves fast user updates coupled with slow network updates in the form of additive increase and multiplicative decrease of the user flows. The proposed algorithm may be viewed as one with fast user update and fast network update that keeps the iterates feasible at all times. Simulations suggest that our proposed algorithm converges faster than the aforementioned benchmark algorithm.
When the flows originate or terminate at a single node, the network problem is the maximization of a so-called d-separable objective function over the bases of a
polymatroid. The solution is the lexicographically optimal base of the
polymatroid. We map the problem of finding the lexicographically optimal base of
a polymatroid to the geometrical problem of finding the concave cover of a set of points on a two-dimensional plane. We also describe an algorithm that finds the concave cover in linear time.
Next, we consider the minimization of a more general objective function, i.e., a separable convex function, over the bases of a polymatroid with a special structure. We propose a novel decomposition algorithm and show the proof of correctness and optimality of the algorithm via the theory of polymatroids. Further, motivated by the need to handle piece-wise linear concave utility functions, we extend the decomposition algorithm to handle the case when the separable convex functions are not continuously differentiable or not strictly convex. We then provide a proof of its correctness and optimality.
18
"Reassessment of the statistical power of published controlled clinical trials." Thesis, 2005. http://library.cuhk.edu.hk/record=b6073998.
Full textAbstract:
Background. The randomized controlled clinical trial is currently the most scientific method for evaluating the effect of medical interventions. The sample size of a trial is crucial for reliably estimating the effect. However, many clinical trials may not be sufficiently large in size to detect the effect of interventions assessed. Previous studies of the statistical power, a relative measure of the largeness of a study, were normally small, mainly examined trials with a statistically insignificant result and were flawed because of the biased or purely hypothetical estimate of the effect for the computation of the power. By using meta-analysis, we conducted this study with improved methods for estimating the power and included a larger number of trials.Findings. A total of 2,923,912 patients from 2,872 clinical trials from 466 systematic reviews were included in the analyses of this thesis. Of the 466 systematic reviews, 24% (113) were identified from the five journals and the remaining 76% (353) were from the Cochrane Library. 1,000 trials and 1,583,204 patients were obtained from 113 systematic reviews identified in the journals, in which 13.7% (95% C.I.: 11.6%, 15.8%) of trials had a sufficient power and the overall power was 34.0% (95% C.I.: 33.7%, 34.3%). 1,872 trials and 1,340,708 patients were obtained from 353 systematic reviews identified in the Cochrane Library, in which 16.7% (95% C.I.: 15.0%, 18.4%) of trials had a sufficient power and the overall power was 37.8% (95% C.I.: 37.6%, 38.0%). (Abstract shortened by UMI.)
Methods. We identified trials from systematic reviews of clinical trials with binary outcomes published in five medical journals and the Cochrane Database of Systematic Reviews. We analyzed the power of trials with a significant result as well as those with an insignificant result. In estimating the power, we used the combined odds ratio of the meta-analysis as the estimate of the effect for trials from systematic reviews with a statistically significant result and a relative risk reduction of 25% for trials from systematic reviews with a statistically insignificant result. In addition to use of the conventional method to estimate the power, we also developed a new "counting method" that does not need any assumption about the effect. Furthermore, the power is also expressed as a relative and absolute difference between the number of subjects required for a power of 80% and that actually recruited by the trials.
Tsoi Kam Fai.
"July 2005."
Adviser: Jin Ling Tang.
Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0161.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (p. 107-113).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.
19
(5930303), Wan-Ting Su. "ANALYTICAL METHODS TO QUANTIFY RISK OF HARM FOR ALERT-OVERRIDDEN HIGH-RISK INTRAVENOUS MEDICATION INFUSIONS." Thesis, 2020.
Find full textAbstract:
The medication errors associated with intravenous (IV) administration may cause severe patient harm. To address this issue, smart infusion pumps now include a built-in dose error reduction system (DERS) to help ensure the safety of IV administration in clinical settings. However, a drug limit alert triggered by DERS may be overridden by the practitioners which can potentially cause patient harm, especially for high-risk medications. Most analytical measures used to estimate the associated risk of harm are frequency-based and only consider the overall drug performance rather than the severity impact from individual alerts. Unlike these other measures, the IV medication harm index attempts to quantify risk of harm for individual alerts. However, it is not known how well these measures describe the risk associated with alert-overridden scenarios. The goal of this research was (1) to quantitatively measure the risk for simulated individual alert-overridden infusions, (2) to compare these assessments against the risk scores obtained among four different analytical methods, and (3) to propose better risk quantification methods with a higher correlation to risk benchmarks than traditional measures, such as the IV Harm index.
In this study, 25 domain experts (20 pharmacists and 5 nurses) were recruited to assess the risk (adjusted for risk benchmarks) for representative scenarios created based on hospital alert data. Four analytical methods were applied to quantify risk for the scenarios: the linear mixed models (Method A), the IV harm index (Method B), Huang and Moh’s matrix-based ranking method matrix-based method (Method C), and the analytical hierarchy process method, adjusted by linear mixed models (Method D). Method A used seven alert factors (identified as key risk factors) to build models for risk prediction, and Methods B and C used two out of seven factors to obtain risk scores. Method D used pairwise comparison surveys to calculate the risk priorities. The quantified scores from the four methods were evaluated in comparison to the risk benchmarks.
Risk assessment results from the domain experts indicated that overdosing scenarios with continuous and bolus dose field limit types had significantly higher risks than those of bolus dose rate type. About the soft limit type, the expected risk in the group with a large soft maximum limit was significantly higher than the group with a small soft maximum limit. This significant difference could be found in the adult intensive care unit (AICU), but not in adult medical/surgical care unit (AMSU). The comparisons between four analytical methods and risk benchmarks showed that the risk scores from Method A (ρ = 0.94) and Method D (ρ = 0.87) were highly correlated to the risk benchmarks. The risk scores derived from Method B and Method C did not have a positive correlation with the benchmarks.
This study demonstrated that the traditional IV harm index should include more risk factors, along with their interaction effects, for increased correlation with risk benchmarks. Furthermore, the linear mixed models and the adjusted AHP method allow for better risk quantification methods where the quantified scores most correlated with the benchmarks. These methods can provide risk-based analytical support to evaluate alert overrides of four high-risk medications, propofol, morphine, insulin, and heparin in the settings of adult intensive care unit (AICU) and adult medical/surgical care unit (AMSU). We believe that healthcare systems can use these analytical methods to efficiently identify the riskiest medication-care unit combinations (e.g. propofol in AICU), and reduce medication error/harm associated with infusions to enhance patient safety.
20
"Proceedings of the tenth international conference Models in developing mathematics education." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-79236.
Full textAbstract:
This volume contains the papers presented at the International Conference on “Models in Developing Mathematics Education” held from September 11-17, 2009 at The University of Applied Sciences, Dresden, Germany. The Conference was organized jointly by The University of Applied Sciences and The Mathematics Education into the 21st Century Project - a non-commercial international educational project founded in 1986. The Mathematics Education into the 21st Century Project is dedicated to the improvement of mathematics education world-wide through the publication and dissemination of innovative ideas. Many prominent mathematics educators have supported and contributed to the project, including the late Hans Freudental, Andrejs Dunkels and Hilary Shuard, as well as Bruce Meserve and Marilyn Suydam, Alan Osborne and Margaret Kasten, Mogens Niss, Tibor Nemetz, Ubi D’Ambrosio, Brian Wilson, Tatsuro Miwa, Henry Pollack, Werner Blum, Roberto Baldino, Waclaw Zawadowski, and many others throughout the world. Information on our project and its future work can be found on Our Project Home Page http://math.unipa.it/~grim/21project.htm
It has been our pleasure to edit all of the papers for these Proceedings. Not all papers are about research in mathematics education, a number of them report on innovative experiences in the classroom and on new technology. We believe that “mathematics education” is fundamentally a “practicum” and in order to be “successful” all new materials, new ideas and new research must be tested and implemented in the classroom, the real “chalk face” of our discipline, and of our profession as mathematics educators. These Proceedings begin with a Plenary Paper and then the contributions of the Principal Authors in alphabetical name order. We sincerely thank all of the contributors for their time and creative effort. It is clear from the variety and quality of the papers that the conference has attracted many innovative mathematics educators from around the world. These Proceedings will therefore be useful in reviewing past work and looking ahead to the future.
21
Paditz, Ludwig, and Alan Rogerson. "Proceedings of the tenth international conference Models in developing mathematics education: September 11 - 17, 2009, Dresden, Saxony, Germany." 2009. https://slub.qucosa.de/id/qucosa%3A1658.
Full textAbstract:
This volume contains the papers presented at the International Conference on “Models in Developing Mathematics Education” held from September 11-17, 2009 at The University of Applied Sciences, Dresden, Germany. The Conference was organized jointly by The University of Applied Sciences and The Mathematics Education into the 21st Century Project - a non-commercial international educational project founded in 1986. The Mathematics Education into the 21st Century Project is dedicated to the improvement of mathematics education world-wide through the publication and dissemination of innovative ideas. Many prominent mathematics educators have supported and contributed to the project, including the late Hans Freudental, Andrejs Dunkels and Hilary Shuard, as well as Bruce Meserve and Marilyn Suydam, Alan Osborne and Margaret Kasten, Mogens Niss, Tibor Nemetz, Ubi D’Ambrosio, Brian Wilson, Tatsuro Miwa, Henry Pollack, Werner Blum, Roberto Baldino, Waclaw Zawadowski, and many others throughout the world. Information on our project and its future work can be found on Our Project Home Page http://math.unipa.it/~grim/21project.htm
It has been our pleasure to edit all of the papers for these Proceedings. Not all papers are about research in mathematics education, a number of them report on innovative experiences in the classroom and on new technology. We believe that “mathematics education” is fundamentally a “practicum” and in order to be “successful” all new materials, new ideas and new research must be tested and implemented in the classroom, the real “chalk face” of our discipline, and of our profession as mathematics educators. These Proceedings begin with a Plenary Paper and then the contributions of the Principal Authors in alphabetical name order. We sincerely thank all of the contributors for their time and creative effort. It is clear from the variety and quality of the papers that the conference has attracted many innovative mathematics educators from around the world. These Proceedings will therefore be useful in reviewing past work and looking ahead to the future.
22
Gad, Mahmoud Attya Mohamed. "Optimalizační problémy při (max,min.)-lineárních omezeních a některé související úlohy." Doctoral thesis, 2015. http://www.nusl.cz/ntk/nusl-336972.
Full textAbstract:
Title: Optimization Problems under (max, min)-Linear Constraints and Some Related Topics. Author: Mahmoud Gad Department/Institue: Department of Probability and Mathematical Statis- tics Supervisor of the doctoral thesis: 1. Prof. RNDr. Karel Zimmermann,DrSc 2. Prof. Dr. Assem Tharwat, Cairo University, Egypt Abstract: Problems on algebraic structures, in which pairs of operations such as (max, +) or (max, min) replace addition and multiplication of the classical linear algebra have appeared in the literature approximately since the sixties of the last century. The first publications on these algebraic structures ap- peared by Shimbel [37] who applied these ideas to communication networks, Cunninghame-Green [12, 13], Vorobjov [40] and Gidffer [18] applied these alge- braic structures to problems of machine-time scheduling. A systematic theory of such algebraic structures was published probable for the first time in [14]. In recently appeared book [4] the readers can find latest results concerning theory and algorithms for (max, +)-linear systems of equations and inequalities. Since operation max replacing addition in no more a group, but a semigroup oppera- tion, it is a substantial difference between solving systems with variables on one side and systems with variables occuring on both sides of the equations....
23
McCanna, David. "Development of Sensitive In Vitro Assays to Assess the Ocular Toxicity Potential of Chemicals and Ophthalmic Products." Thesis, 2009. http://hdl.handle.net/10012/4338.
Full textAbstract:
The utilization of in vitro tests with a tiered testing strategy for detection of mild ocular irritants can reduce the use of animals for testing, provide mechanistic data on toxic effects, and reduce the uncertainty associated with dose selection for clinical trials. The first section of this thesis describes how in vitro methods can be used to improve the prediction of the toxicity of chemicals and ophthalmic products. The proper utilization of in vitro methods can accurately predict toxic threshold levels and reduce animal use in product development. Sections two, three and four describe the development of new sensitive in vitro methods for predicting ocular toxicity. Maintaining the barrier function of the cornea is critical for the prevention of the penetration of infections microorganisms and irritating chemicals into the eye. Chapter 2 describes the development of a method for assessing the effects of chemicals on tight junctions using a human corneal epithelial and canine kidney epithelial cell line. In Chapter 3 a method that uses a primary organ culture for assessing single instillation and multiple instillation toxic effects is described. The ScanTox system was shown to be an ideal system to monitor the toxic effects over time as multiple readings can be taken of treated bovine lenses using the nondestructive method of assessing for the lens optical quality. Confirmations of toxic effects were made with the utilization of the viability dye alamarBlue. Chapter 4 describes the development of sensitive in vitro assays for detecting ocular toxicity by measuring the effects of chemicals on the mitochondrial integrity of bovine cornea, bovine lens epithelium and corneal epithelial cells, using fluorescent dyes.
The goal of this research was to develop an in vitro test battery that can be used to accurately predict the ocular toxicity of new chemicals and ophthalmic formulations. By comparing the toxicity seen in vivo animals and humans with the toxicity response in these new in vitro methods, it was demonstrated that these in vitro methods can be utilized in a tiered testing strategy in the development of new chemicals and ophthalmic formulations.