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A study of improving the reliability of the Cochrane risk of bias tool for assessing validity of clinical trials: 一個用於提高考柯藍風險評價工具信度的評價臨床試驗偏倚風險的研究 / 一個用於提高考柯藍風險評價工具信度的評價臨床試驗偏倚風險的研究 / CUHK electronic theses & dissertations collection / study of improving the reliability of the Cochrane risk of bias tool for assessing validity of clinical trials: Yi ge yong yu ti gao Kaokelan feng xian ping jia gong ju xin du de ping jia lin chuang shi yan pian yi feng xian de yan jiu / Yi ge yong yu ti gao Kaokelan feng xian ping jia gong ju xin du de ping jia lin chuang shi yan pian yi feng xian de yan jiuJanuary 2014 (has links)
Objective. The Cochrane risk of bias tool (CRoB) is one of the most widely used tools for assessing the risk of bias of clinical trials. However, it was criticized for its poor inter-rater reliability, lack of clear and detailed guidelines for its application, and no clear distinguishing between reporting quality from real quality in implementation. This study aims to develop a framework (or improved CRoB, iCRoB) so as to improve the inter-rater reliability of the CRoB in its first 4 domains: sequence generation, allocation concealment, blinding of participants and personnel, and blinding of outcome assessment, through providing: i) a structured pathway for assessing risk of bias assessment; and ii) a comprehensive dictionary of scenarios for each domain. / Methods. The study is consisted of 4 steps: / i) Step 1: Develop a step-by-step structured pathway for assessing the risk of bias. / ii) Step 2: Identify and summarize possible scenarios that are used in literature to describe a domain in clinical trials by using a qualitative content analysis approach. A random sample of 100 Cochrane systematic reviews (SRs) was taken from the Cochrane Database of Systematic Reviews. Each review was carefully scrutinized for this purpose. / iii) Step 3: Merge the scenarios identified from the sample with those already provided in the CRoB. The combined list of scenarios extends the current coverage of the CRoB and forms a more comprehensive dictionary of scenarios for use in the future. The bias assessment pathway and the new dictionary of scenarios in combination are the new components added or contribution to the CRoB to form the iCRoB. / v) Step 4: Conduct a randomized controlled study that allocated at random 8 raters equally into either using the CRoB or our new iCRoB. 150 clinical trials were randomly selected from the fore-mentioned 100 SRs for the inter-rater reliability comparison. Both inter-rater reliability among individual raters (measured with Fleiss’ κ) and that across rater pairs (measured with weighted Cohen’s κ) were computed. Data analyses were conducted by using STATA version 13.0. / Results. A structured pathway for systematically assessing bias was designed, which helps classify a study into one of 5 categories for each risk of bias domain based on the information provided in the report of a trial: Category A: a trial reports in details how a bias reduction method was conducted and it is also deemed by the assessor to be conducted adequately; Category B: a trial reports in details how a bias reduction method was conducted but it is deemed by the assessor to be conducted inadequately; Category C: a trial reports that a bias reduction method was conducted but no detailed description was given which can be used to judge whether it was done adequately; Category D: a trial reports that a bias reduction method was not conducted; Category E: a trial does not mention at all whether or not a bias reduction method was conducted. / A total of 34, 36, 26 and 20 scenarios were generated for sequence generation, allocation concealment, blinding of participants and personnel, and blinding of outcome assessment, respectively. We extended the current CRoB list of scenarios by a number of 20, 23, 26 and 20 respectively for the 4 bias reduction domains. / Our trial results showed that the iCRoB had a higher inter-rater reliability across rater pairs than the original CRoB for every bias reduction domain. The weighted κ was 0.71 and 0.81 for sequence generation respectively for CRoB and iCRoB; 0.53 and 0.61 for allocation concealment respectively for CRoB and iCRoB; 0.56 for blinding of participants and personnel in CRoB, 0.68 for blinding of participants and 0.70 for blinding of personnel ini CRoB; and 0.19 and 0.43 for blinding of outcome assessment respectively for CRoB and iCRoB. / Conclusion. We developed the iCRoB including a standard pathway and extended substantively the dictionary of scenarios for making the judgement on risk of bias in the reports of clinical trials. Our iCRoB showed a higher reliability than the current CRoB in all the domains examined. The iCRoB can be recommended for improving the assessment of bias in clinical trials. / 目的:考柯藍偏倚風險評估工具(CRoB)是最廣泛應用的用於評價臨床試驗偏倚風險的工具之一。然而,CRoB 有以下三個缺陷:評價者間信度低,缺乏明確和詳細的應用說明和沒有明確區分報告質量和方法學質量。本研究擬制定一個新的工具iCRoB 用以提高CRoB 前4 項指標的評價者間信度。這4項指標分別為隨機序列生成,分配隱藏,對研究對象和研究者實施盲法,和對結局評估者實施盲法。本研究通過以下2 點實現這一目的:i) 提供一個結構化路徑用以評估偏倚風險;ii) 為每個研究指標提供一個廣泛包含偏倚風險評估相關描述場景的字典。 / 方法:本研究包含以下4 個步驟: / 第1 步:制定一個用以評估偏倚風險的結構化路徑。 / 第2 步:從考柯藍系統綜述數據庫中隨機抽取100 篇系統綜述,應用定性內容分析法從中確定並總結出臨床試驗中與偏倚風險相關的可能的描述場景。 / 第3 步:將從100 個樣本中總結的描述場景與CRoB 中已有的場景合併,從而擴大CRoB 的描述場景的覆蓋範圍,得到一個更廣泛包含偏倚風險評估相關描述場景字典。偏倚風險評估的結構化路徑和包含場景描述的字典共同形成了本研究中新制定的iCRoB,用以評估臨床試驗的偏倚風險。 / 第4 步:在一個隨機對照研究中,8 名評價者被隨機平均分配至CRoB 組或者iCRoB 組。在上述100個系統綜述所納入的臨床試驗中隨機抽取150 個臨床試驗用以比較CRoB 和iCRoB 的評價者間信度。評價者間信度的比較包括個體評價者間信度(用Fleiss’κ 測量)和配對評價者間信度(用加權Cohen’s κ 測量)的比較。數據採用Stata 13.0 進行統計分析。 / 結果:本研究成功的制定了一個用於系統評價偏倚風險的結構化路徑,在該結構化路徑中,每個偏倚風險相關的指標在一個臨床研究中將分為以下5 類: / A 類:臨床試驗詳細描述了預防偏倚的措施的實施,根據描述可以判定該措施的實施能預防偏倚的產生; B 類:臨床試驗詳細描述了預防偏倚的措施的實施,根據描述可以判定該措施的實施不能預防偏倚的產生; C 類:臨床試驗報告採取了預防偏倚的措施,但未描述這一過程如何實施,從而無法判斷其實施是否正確; D 類:臨床試驗報告沒有採取任何預防偏倚的措施; E 類:臨床試驗沒有報告是否採取了預防偏倚的措施。 / 本研究分別為隨機序列生成,分配隱藏,對研究對象和研究者實施盲法,和對結局評估者實施盲法收集了34,36,26 和20 個描述場景。與CRoB 提供的描述場景比較,iCRoB 分別為隨機序列生成,分配隱藏,對研究對象和研究者實施盲法,和對結局評估者實施盲法增加了20,23,26 和20 個新的描述場景。 / 隨機對照試驗結果顯示,iCRoB 中每個研究指標的配對評價者間信度均高於CRoB,其中,隨機序列生成加權κ 為0.71(CRoB)和0.81(iCRoB),分配隱藏加權κ 為0.53(CRoB)和0.61(iCRoB),對研究對象和研究者實施盲法加權κ 為0.56(CRoB),對研究對象實施盲法加權κ 為0.68(iCRoB),對研究者實施盲法加權κ 為0.70(iCRoB),對結局評估者實施盲法加權κ 為0.19(CRoB)和0.43(iCRoB)。 / 結論:本研究通過制定一個由偏倚風險評估的結構化路徑和包含場景描述的字典組成的iCRoB,用以改善CRoB 中對臨床試驗中隨機序列生成,分配隱藏,對研究對象和研究者實施盲法,和對結局評估者實施盲法偏倚風險評估過程。相比於CRoB,iCRoB 在每個研究指標中均顯示出更好的配對評價者間信度。這些結果證明評價者間信度可以通過提供結構化偏倚風險評估路徑和更全面的描述場景字典而提高。 / Wu, Xinyin. / Thesis Ph.D. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 93-105). / Abstracts also in Chinese. / Title from PDF title page (viewed on 09, September, 2016). / Wu, Xinyin. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.y066 / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.
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Complex medical event detection using temporal constraint reasoningGao, Feng January 2010 (has links)
The Neonatal Intensive Care Unit (NICU) is a hospital ward specializing in looking after premature and ill newborn babies. Working in such a busy and complex environment is not easy and sophisticated equipment is used to help the daily work of the medical staff . Computers are used to analyse the large amount of monitored data and extract hidden information, e.g. to detect interesting events. Unfortunately, one group of important events lacks features that are recognizable by computers. This group includes the actions taken by the medical sta , for example two actions related to the respiratory system: inserting an endotracheal tube into a baby’s trachea (ET Intubating) or sucking out the tube (ET Suctioning). These events are very important building blocks for other computer applications aimed at helping the sta . In this research, a strategy for detecting these medical actions based on contextual knowledge is proposed. This contextual knowledge specifies what other events normally occur with each target event and how they are temporally related to each other. The idea behind this strategy is that all medical actions are taken for di erent purposes hence may have di erent procedures (contextual knowledge) for performing them. This contextual knowledge is modelled using a point based framework with special attention given to various types of uncertainty. Event detection consists in searching for consistent matching between a model based on the contextual knowledge and the observed event instances - a Temporal Constraint Satisfaction Problem (TCSP). The strategy is evaluated by detecting ET Intubating and ET Suctioning events, using a specially collected NICU monitoring dataset. The results of this evaluation are encouraging and show that the strategy is capable of detecting complex events in an NICU.
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Online Learning Techniques for Improving Robot Navigation in Unfamiliar DomainsSofman, Boris 01 December 2010 (has links)
Many mobile robot applications require robots to act safely and intelligently in complex unfamiliarenvironments with little structure and limited or unavailable human supervision. As arobot is forced to operate in an environment that it was not engineered or trained for, various aspectsof its performance will inevitably degrade. Roboticists equip robots with powerful sensorsand data sources to deal with uncertainty, only to discover that the robots are able to make onlyminimal use of this data and still find themselves in trouble. Similarly, roboticists develop andtrain their robots in representative areas, only to discover that they encounter new situations thatare not in their experience base. Small problems resulting in mildly sub-optimal performance areoften tolerable, but major failures resulting in vehicle loss or compromised human safety are not.This thesis presents a series of online algorithms to enable a mobile robot to better deal withuncertainty in unfamiliar domains in order to improve its navigational abilities, better utilizeavailable data and resources and reduce risk to the vehicle. We validate these algorithms throughextensive testing onboard large mobile robot systems and argue how such approaches can increasethe reliability and robustness of mobile robots, bringing them closer to the capabilitiesrequired for many real-world applications.
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A joint model for longitudinal data and competing risks /Jaros, Mark J. January 2008 (has links)
Thesis (Ph.D. in Biostatistics) -- University of Colorado Denver, 2008. / Typescript. Includes bibliographical references (leaves 117-119). Free to UCD Anschutz Medical Campus. Online version available via ProQuest Digital Dissertations;
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Radial basis function interpolationDu Toit, Wilna 03 1900 (has links)
Thesis (MSc (Applied Mathematics))--Stellenbosch University, 2008. / A popular method for interpolating multidimensional scattered data is using
radial basis functions. In this thesis we present the basic theory of radial basis
function interpolation and also regard the solvability and stability of the
method. Solving the interpolant directly has a high computational cost for
large datasets, hence using numerical methods to approximate the interpolant
is necessary. We consider some recent numerical algorithms. Software to implement
radial basis function interpolation and to display the 3D interpolants
obtained, is developed. We present results obtained from using our implementation
for radial basis functions on GIS and 3D face data as well as an image
warping application.
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Análise multinível da cobertura vacinal no Município de São Paulo / Multilevel analysis of immunization coverage in São Paulo CityManoel Carlos Sampaio de Almeida Ribeiro 10 August 2005 (has links)
Vigilância Epidemiológica, é a forma através do qual o SUS busca produzir impacto em termos de controle, eliminação e até erradicação de um conjunto definido de doenças imunopreveníveis. O PNI tem conseguindo bons resultados em termos de cobertura vacinais e controle de importantes doenças, embora ainda com importantes desigualdades regionais e locais. Este estudo busca conhecer os fatores que determinam a efetividade deste programa no município de São Paulo a partir de uma análise mutinível. MÉTODO: Em 2002 o Depto. de Medicina Social da FCMSCSP realizou o Inquérito de Cobertura Vacinal no primeiro ano de vida para a coorte de nascidos entre 1º de novembro de 1999 e 31 de outubro de 2000 residentes no município de São Paulo. Este inquérito domiciliar se baseou no processo de amostragem por conglomerado preconizado pela OPAS. Em cada um dos 41 Distritos de Saúde (DS) foi calculada uma amostra de 210 crianças, num total de 8610 crianças. A importância de variáveis grupais e individuais em relação a cobertura vacinal para esquema completo em crianças com um ano de idade e a participação no Dia Nacional de Vacinação (25/08/2001) foi investigada através de um modelo multinível logístico. Foram estabelecidos nesta análise três níveis: individual, conglomerado, compostos pelos setores censitários e decorrentes do processo de análise e o DS. O modelo multinível foi construído através do software MLWin 2.0. RESULTADOS: O modelo multinível para cobertura com esquema completo em crianças com um ano de idade evidenciou um efeito do DS de 0,15 com um p <0,01; um efeito do conglomerado de 0,07 e p=0,051.A inclusão das variáveis individuais quase não alterou os efeitos aleatórios dos dois níveis. No modelo final as seguintes variáveis mostraram-se associadas ao desfecho: uso de serviço privado OR de 0,64 (IC95%0,50-0,82), pessoas por cômodo um OR de 0,93 (IC95%;0,88-0,98), mãe trabalhar fora e escolaridade da mãe estiveram associadas ao desfecho e apresentaram uma interação.Os dados sugerem uma tendência de aumento da cobertura vacinal conforme aumenta a escolaridade da mãe até a categoria de 9 a 11 anos, voltando a ser menor em crianças com mães um nível de estudo maior. Em relação a participação em campanha de vacinação, o nível do DS apresentou um efeito de 0,32, e nível do conglomerado de 0,18 (p<0,001). Em relação as variáveis individuais, uso de serviço privado para vacinar apresentou um OR de 0,26 (IC95%: 0,21-0,36), mãe trabalha fora de casa um OR de 0,82 (IC95%:0,73-0,92) A escolaridade da mãe, usando a faixa de 9 a 11 anos de escolaridade da mãe por referência, apresentou até a terceira série OR de 0,97 (IC95%: 0,76-1,23), de 4 a 8 anos um OR de 0,86 (IC95%:0,75-0,98) e mais 12 anos de estudo um OR de 0,54 (IC95%:0,44-0,66). A participação em campanha foi maior conglomerados com menor renda média do chefe e no DS com maior proporção de pobres. CONCLUSÕES: Existem diferenças em relação à cobertura vacinal no município de São Paulo que não são totalmente explicadas pelas características individuais e familiares. O DS de moradia destas famílias possui um efeito de contexto sobre a cobertura vacinal. A participação em campanhas de vacinação se revela uma importante estratégia para o acesso dos segmentos menos favorecidos às vacinas. É necessário também aprofundar o conhecimento sobre a cobertura vacinal nos segmentos mais abastados do município / INTRODUCTION: In Brazil, the National Immunization Program (PNI), a branch of the National Surveillance System, is the standard approach of the Brazilian Unified Health System to control, eliminate and even eradicate a set of vaccine-preventable diseases. The PNI has attained good results in terms of vaccine coverage and controlling important diseases, although local and regional inequalities persist. This study aimed to identify which factors were influencing the effectiveness of immunization program in São Paulo City, using multilevel analysis. METHODS: In 2002 the Social Medicine Department of Santa Casa School of Medical Sciences (FCMSC) carried out a vaccine coverage survey, among residents of São Paulo City, addressing the vaccines recommended for the first year of life, among children born between November 1 of 1999 and October 31 of 2000. This household survey was done using the cluster sample technique advocated by the PAHO. In each one of the 41 Health Districts (DS) a sample of 210 infants, in a gross one of 8610, was obtained. The role of group and individuals variable levels in the vaccine coverage for the complete schedule among infants of one year of age and the participation in the National Vaccination Day (25/08/2001) were investigated through a logistic multilevel model. The analysis was performed including three levels: individual, cluster and health districts (DS). The cluster was based on the census tracts, defined by the sampling procedures. The multilevel model was performed using MLWin 2.0. software. RESULTS: The multilevel model for complete coverage with the recommended vaccines for the age group (children aged up to one year), identified at the health district (DS) an effect of 0,15 (p-value <0,01) and at the cluster level an effect of 0,07 (p=0,051). Adding individual level variables did not change the random effects of the two other levels. The final model included the following variables associated to the outcome: use of private service , (OR= 0,64, 95%CI: 0,50-0,82), number of persons by room (agglomerate), (OR= 0,93, 95%CI: 0,88-0,98). The employment status of the mother and mother\'s level of education, were both associated to the outcome and presented an interaction. Our data suggests the immunization uptake increases as the mother\'s years of education increases up to 9 to 11 years, decreasing among children whose mothers have greater level than 11 years of schooling. Regarding participation in vaccination campaign, at the DS level, the effect was 0,32, and at the cluster level the effect was 0,18 (p<0,001). At the individual level, the following characteristics were associated to the outcome: use of private clinic for vaccination (OR=0,26, 95% CI: 0,21-0,36), a working mother (OR=0,82, 95% CI:0,73-0,92). To examine the effect of mother\'s education, we used 9 to 11 years of education as the reference category. For children whose mothers had up to 3 years of education the OR was 0,97 (95% CI: 0,76-1,23); from 4 to 8 years of education the OR was 0,86 (95% CI:0,75-0,98) and for more than 12 years of study an OR of 0,54 (95% CI:0,44-0,66). The participation in campaign was bigger in clusters with lower head of household income, and bigger proportion of poor population. CONCLUSIONS: There are differences in the immunization uptake in São Paulo City that cannot be fully explained by the family and individual characteristics. The Health District, a geographic area where the household is located, poses a context effect on the vaccine coverage. Vaccine campaigns have an important role in increasing the access to vaccines for the poorest population. It is necessary further studies to a better understanding of the vaccine coverage in the wealthier segments of the town
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"Avaliação do perfil epidemiológico e clínico de portadoras de endometriose pélvica e identificação dos principais fatores de risco relacionados à doença obtidos através de questionário interativo" / Epidemiological and clinical profiles in patients with pelvic endometriosis and identification of main risk factors related to the disease through an interactive program of women health integral assistanceNeme, Rosa Maria 01 March 2005 (has links)
A endometriose representa uma das doenças mais prevalentes em ginecologia, e afeta cerca de 10 a 15% das mulheres em idade reprodutiva. Apesar do grande aumento da ocorrência desta doença, pouco se sabe sobre sua epidemiologia, principalmente devido à dificuldade metodológica por tratar-se de patologia de definição e etiologia desconhecidas. A prevalência estimada varia de 4% entre mulheres assintomáticas a cerca de 50% entre adolescentes com dismenorréia incapacitante. Fatores de risco pessoais foram descritos, como idade, estado sócio-econômico, estado civil, fatores menstruais, como duração e intervalo dos ciclos e idade da menarca. Sintomas como dismenorréia, dor acíclica, dispareunia de profundidade, alterações urinárias e intestinais cíclicas e infertilidade, também são associados à doença. O objetivo do presente estudo foi determinar uma forma de predizer o diagnóstico cirúrgico baseado no perfil epidemiológico e sintomas da endometriose, através da utilização de um programa interativo para este cálculo. Para tal, analisou-se mulheres com diagnóstico histológico da doença e pacientes sem diagnóstico, pertencentes ao Ambulatório de Ginecologia Preventiva do HC-FMUSP (grupo controle), analisadas através deste programa interativo, constituindo amostra de 1872 pacientes estudadas. A avaliação estatística foi realizada pelos testes do qui-quadrado, t-Student e regressão logística multifatorial. Encontrou-se como fatores de risco significativos a idade, raça, grau de instrução, estado civil, intervalo do ciclo menstrual, presença de dismenorréia, alterações urinárias cíclicas, tipo de infertilidade, além de sintomas mais específicos como disúria, proctorragia e diarréia, dados que foram aplicados através do programa informatizado. Concluiu-se que tal modelo apresenta grande valor para a análise da razão de chances de ocorrência de endometriose na população geral. Análises prospectivas tornam-se imperativas a fim de testarmos tal modelo preditivo para estabelecermos parâmetros que conduziriam ou não à realização de um procedimento invasivo para o diagnóstico da doença. / Advances in understanding the epidemiology of endometriosis have lagged behind other diseases. To determine whether the surgical diagnosis of endometriosis can be predicted using noninvasive tools as epidemiological profile, medical history and symptoms related to the disease, were analyzed women with histological diagnosis of endometriosis and patients without diagnosis, analyzed through an interactive program, constituting a sample of 1872 studied patients. We could conclude that such model presents big value for the analysis of odds ratio to endometriosis in general population. Prospective analysis become imperative in order to create a predictive model to establish parameters that could suggest a surgical procedure.
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Computational techniques for statistical morphometric analysis of 3-D MRI data of human skull and brain. / 統計形態分析之計算方法及其核磁共振影像應用 / Computational techniques for statistical morphometric analysis of three-dimensional MRI data of human skull and brain / CUHK electronic theses & dissertations collection / Tong ji xing tai fen xi zhi ji suan fang fa ji qi he ci gong zhen ying xiang ying yongJanuary 2008 (has links)
Shi, Lin. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 171-185). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese.
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The applications of image processing in biology and relevant data analysis.January 2007 (has links)
Wang, Zexi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 63-64). / Abstract --- p.i / Acknowledgement --- p.iii / Chapter 0 --- Introduction --- p.1 / Chapter 1 --- The Design of the Experiments --- p.4 / Chapter 1.1 --- Flies and the Devices --- p.5 / Chapter 1.2 --- Parameter Settings and Interested Information --- p.8 / Chapter 2 --- Video Processing --- p.11 / Chapter 2.1 --- "Videos, Computer Vision and Image Processing" --- p.11 / Chapter 2.2 --- Details in Video Processing --- p.14 / Chapter 3 --- Data Analysis --- p.20 / Chapter 3.1 --- Background --- p.20 / Chapter 3.2 --- Outline of Data Analysis in Our Project --- p.22 / Chapter 4 --- Effect of the Medicine --- p.25 / Chapter 4.1 --- Hypothesis Testing --- p.26 / Chapter 4.2 --- Two-sample t Test --- p.28 / Chapter 5 --- Significance of the Two Factors --- p.32 / Chapter 5.1 --- Background of ANOVA --- p.33 / Chapter 5.2 --- The Model of ANOVA --- p.35 / Chapter 5.3 --- Two-way ANOVA in Our Data Analysis --- p.42 / Chapter 6 --- Regression Model --- p.45 / Chapter 6.1 --- Background of Regression Analysis --- p.47 / Chapter 6.2 --- Polynomial Regression Models --- p.52 / Chapter 6.2.1 --- Background --- p.52 / Chapter 6.2.2 --- R2 and adjusted R2 --- p.53 / Chapter 6.3 --- Model Verification --- p.58 / Chapter 6.4 --- A Simpler Model As the Other Choice --- p.59 / Chapter 6.5 --- Conclusions --- p.60 / Chapter 7 --- Further Studies --- p.61 / Bibliography --- p.62
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ANALYSIS AND INTERPRETATION OF 2D/3D SEISMIC DATA OVER DHURNAL OIL FIELD, NORTHERN PAKISTANAfsar, Fatima January 2013 (has links)
The study area, Dhurnal oil field, is located 74 km southwest of Islamabad in the Potwar basin of Pakistan. Discovered in March 1984, the field was developed with four producing wells and three water injection wells. Three main limestone reservoirs of Eocene and Paleocene ages are present in this field. These limestone reservoirs are tectonically fractured and all the production is derived from these fractures. The overlying claystone formation of Miocene age provides vertical and lateral seal to the Paleocene and Permian carbonates. The field started production in May 1984, reaching a maximum rate of 19370 BOPD in November 1989. Currently Dhurnal‐1 (D-1) and Dhurnal‐6 (D-6) wells are producing 135 BOPD and 0.65 MMCF/D gas. The field has depleted after producing over 50 million Bbls of oil and 130 BCF of gas from naturally fractured low energy shelf carbonates of the Eocene, Paleocene and Permian reservoirs. Preliminary geological and geophysical data evaluation of Dhurnal field revealed the presence of an up-dip anticlinal structure between D-1 and D-6 wells, seen on new 2003 reprocessed data. However, this structural impression is not observed on old 1987 processed data. The aim of this research is to compare and evaluate old and new reprocessed data in order to identify possible factors affecting the structural configuration. For this purpose, a detailed interpretation of old and new reprocessed data is carried out and results clearly demonstrate that structural compartmentalization exists in Dhurnal field (based on 2003 data). Therefore, to further analyse the available data sets, processing sequences pertaining to both vintages have been examined. After great effort and detailed investigation, it is concluded that the major parameter giving rise to this data discrepancy is the velocity analysis done with different gridding intervals. The detailed and dense velocity analysis carried out on the data in 2003 was able to image the subtle anticlinal feature, which was missed on the 1987 processed seismic data due to sparse gridding. In addition to this, about 105 sq.km 3D seismic data recently (2009) acquired by Ocean Pakistan Limited (OPL) is also interpreted in this project to gain greater confidence on the results. The 3D geophysical interpretation confirmed the findings and aided in accurately mapping the remaining hydrocarbon potential of Dhurnal field.
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