• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 112
  • 102
  • 40
  • 19
  • 17
  • 8
  • 7
  • 5
  • 4
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 372
  • 170
  • 84
  • 77
  • 66
  • 55
  • 49
  • 47
  • 41
  • 36
  • 34
  • 32
  • 30
  • 27
  • 26
  • 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.
71

Control charts applying a sequential test at fixed sampling intervals with optional sampling at fixed times

Stoumbos, Zachary G. 13 July 2007 (has links)
In recent years, variable sampling interval (VSI) control charts have been intensively investigated. In contrast to traditional fixed sampling interval (FSI) control charts, VSI charts vary the sampling interval as a function of the data. VSI charts detect many process changes faster than their FSI counterparts. A disadvantage, however, of VSI charts as recently formulated is that the advance prediction of sampling times is impossible for more than the next sample. A control chart is proposed which applies a sequential probability ratio test (SPRT) at fixed sampling intervals, the SPRT chart, to monitor the mean of a process with a normal distribution. A natural modification of the SPRT chart, the SPRT chart with sampling at fired times (SFT), is also proposed in which samples are always taken at pre-specified, equally spaced fixed times, with additional samples taken between these times as indicated by the data. A third control chart is introduced as a generalization of the VSI cumulative sum (CUSUM) chart that uses two sampling intervals, called the universal CUSUM (UC) chart, in order to address the need for a general framework for the study of control charts that are equivalent to a sequence of SPRT’s. The UC chart can also be viewed as a generalization of the SPRT chart. The integral equation approach is adapted for the evaluation of properties of both the unmodified and modified with SFT versions of the SPRT chart, such as average time to signal (ATS), steady state ATS (SSATS), and average number of observations to signal (ANOS). After comparisons are performed within the general framework of the UC chart, the unmodified SPRT chart is found to be more efficient than both the FSI and VSI X charts and the FSI CUSUM chart, though very similar in efficiency to the VSI CUSUM chart. The modified SPRT chart with SFT is found to be more efficient than all five of the other control charts, including its unmodified version and the VSI CUSUM chart. General guidelines are provided for the design of both versions of the SPRT chart. / Ph. D.
72

A robust Shewhart control chart adjustment strategy

Zou, Xueli 06 June 2008 (has links)
The standard Shewhart control chart for monitoring process stability is generalized by selecting a point in time at which the distance between the control limits is reduced. Three cost models are developed to describe the total cost per unit time of monitoring the mean of a process using both the standard and the generalized Shewhart control chart. The cost models are developed under the assumption that the quality characteristic of interest is normally distributed with known and constant variance. In the development of the first model, the negative exponential distribution is employed to model the time to process shift. Then, the uniform distribution and the Weibull distribution are used for the same purpose in the second and the third model, respectively. The motivation for this effort is to increase chart sensitivity to small but anticipated shifts in the process average. Cost models are constructed to allow the optimal choice of change over time and the best values for the initial and adjusted control limit values. The cost models are analyzed to determine the optimal control chart parameters including those associated with both the standard and the generalized control chart. The models are also used to provide a comparison with conventional implementation of the control chart. It is shown that the proposed cost models are efficient and economical. Figures and tables are provided to aid in the design of models for both the standard and the generalized Shewhart control chart. / Ph. D.
73

Control chart procedures based on cumulative gauging scores

Chung, Jain January 1985 (has links)
Control charts based on cumulative gauging scores rely on gauge scoring systems used for transforming actual observations into integer gauging scores. In some cases, the gauging scores are easy to obtain by using a mechanical device such as in the go-no-go inspection process. Thus, accurate measurements of selected quality characteristics are not necessary. Also, different control purposes can be achieved p by using different scoring systems. Cumulative gauging score charts based on two pairs of gauges are proposed to control the process mean or the standard deviation by either gauging one or several observations. Both random walk and cusum type cumulative gauging score charts are used. For controlling the process mean and standard deviation at the same time, a cusum type and a two-dimensional random walk type procedure are proposed. A gauging scheme can be applied to multivariate quality control by gauging either x² or T² statistics. A simple multivariate control chart which is based on the multivariate sign score vector is also proposed. The exact run length distribution of these cumulative gauging score charts can be obtained by formulating the procedures as Markov chain processes. For some procedures, the average run length (ARL) can be obtained in a closed form expression by solving a system of difference equations with appropriate boundary conditions. Comparisons based on the ARL show that the cumulative gauging score charts can detect small shifts in the quality characteristic more quickly than the Shewhart type X-chart. The efficiency of the cusum type gauging score chart is close to the regular CUSUM chart. The random walk type gauging score chart is more robust than the Shewhart and CUSUM charts to observations which have heavy a tailed distribution or which are serially correlated. For multivariate quality control. A procedure based on gauging the x² statistic has better performance than the x² chart. Also, a new multivariate control chart procedure which is more robust to the misspecification of the correlation than the x² chart is proposed. / Ph. D.
74

En jämförande studie mellan olika JavaScriptbibliotek för visualisering : Prestandamätning av JavaScriptbibliotek för statistiska grafer och diagram / A comparative study between different JavaScript libraries for visualization : Performance measurements of JavaScript libraries for statistical graphs and diagrams

Carlström, Alice January 2018 (has links)
Visualisering av statistik är ett tydligt sätt att presentera data som annars kan ses som svår att tyda och analysera. Med hjälp av visualiseringar på webben kan man nå ut till många och det är ett smidigt sätt att ta med sig och dela med sig av information. Denna rapport bygger på ett experiment där olika JavaScriptbibliotek jämförs baserat på tiden det tar att rita ut diagram av olika storlekar och typer. Linjediagram, punktdiagram och stapeldiagram skapas med de olika biblioteken. Vilka bibliotek som jämförs väljs ut utifrån ett antal kriterier och Chart.js, Google Charts och Plotly.js är de som uppfyller alla krav. Undersökningar där utritningstiden mäts genomförs och resultaten visar att Chart.js är snabbast på att rita ut diagram i de flesta mätningarna. Det finns signifikanta skillnader mellan alla diagrammätningar förutom mellan Linjediagram 2 skapat med Chart.js och Linjediagram 2 skapat med Plotly.js samt Plotly.js Stapeldiagram 1 och Plotly.js Stapeldiagram 5. Mätningarna visar också att diagram som baseras på större datamängd, i de flesta fall, också har längre utritningstid än diagram baserade på mindre datamängd.
75

Determining the most appropiate [sic] sampling interval for a Shewhart X-chart

Vining, G. Geoffrey January 1986 (has links)
A common problem encountered in practice is determining when it is appropriate to change the sampling interval for control charts. This thesis examines this problem for Shewhart X̅ charts. Duncan's economic model (1956) is used to develop a relationship between the most appropriate sampling interval and the present rate of"disturbances,” where a disturbance is a shift to an out of control state. A procedure is proposed which switches the interval to convenient values whenever a shift in the rate of disturbances is detected. An example using simulation demonstrates the procedure. / M.S.
76

The Fixed v. Variable Sampling Interval Shewhart X-Bar Control Chart in the Presence of Positively Autocorrelated Data

Harvey, Martha M. (Martha Mattern) 05 1900 (has links)
This study uses simulation to examine differences between fixed sampling interval (FSI) and variable sampling interval (VSI) Shewhart X-bar control charts for processes that produce positively autocorrelated data. The influence of sample size (1 and 5), autocorrelation parameter, shift in process mean, and length of time between samples is investigated by comparing average time (ATS) and average number of samples (ANSS) to produce an out of control signal for FSI and VSI Shewhart X-bar charts. These comparisons are conducted in two ways: control chart limits pre-set at ±3σ_x / √n and limits computed from the sampling process. Proper interpretation of the Shewhart X-bar chart requires the assumption that observations are statistically independent; however, process data are often autocorrelated over time. Results of this study indicate that increasing the time between samples decreases the effect of positive autocorrelation between samples. Thus, with sufficient time between samples the assumption of independence is essentially not violated. Samples of size 5 produce a faster signal than samples of size 1 with both the FSI and VSI Shewhart X-bar chart when positive autocorrelation is present. However, samples of size 5 require the same time when the data are independent, indicating that this effect is a result of autocorrelation. This research determined that the VSI Shewhart X-bar chart signals increasingly faster than the corresponding FSI chart as the shift in the process mean increases. If the process is likely to exhibit a large shift in the mean, then the VSI technique is recommended. But the faster signaling time of the VSI chart is undesirable when the process is operating on target. However, if the control limits are estimated from process samples, results show that when the process is in control the ARL for the FSI and the ANSS for the VSI are approximately the same, and exceed the expected value when the limits are fixed.
77

Karinių aeronavigacinių žemėlapių optimizavimas / Optimization of military airnavigation charts

Ovodas, Donatas 27 December 2012 (has links)
Disertaciniame darbe pasitelkiant kompleksinė vertinimo metodika analizuojami karinių aeronavigacinių žemėlapių ženklai, ženklų sistemos ir užrašai. Šios analizės pagrindu tobulinami sutartiniai ženklai, optimizuojamas žemėlapio turinys ir pateikiama vieningos Lietuvos karo aeronavigacinių duomenų bazės struktūrą. Kompleksiškai parengta tyrimo metodika rėmėsi Lietuvoje nusistovėjusia teminių žemėlapių ir ženklų kartosemiotine vertinimo praktika. Įvairūs ženklų ir užrašų vertinimo aspektai leido tiksliai ir nuodugniai atlikti aeronavigacinių ženklų ir užrašų vertinimą. Analizės metu nustatyta kad ne visi karinių aeronavigacinių žemėlapių ženklai atitinka kartosemiotikos reikalavimų, todėl galėtu būti keičiami. Karinių aeronavigacinių ženklų analizė ir tobulinimas rėmėsi ankščiau vykdytais psichofiziologinio suvokimo tyrimais bei išvadomis. Siūlomi nauji aeronavigacinių žemėlapių ženklai pilnai atitinka psichofiziologinių tyrimų rekomendacijas. Išnagrinėjus karinius NATO šalių aeronavigacinius žemėlapius ir atsižvelgiant į vieningą žemėlapių sistemą, klasifikacijos požymius ir atitinkamus klasifikacijų reikalavimus, darbe pateikta apibendrinta NATO šalių karinių aeronavigacinių žemėlapių klasifikacija, kurioje yra numatyta galimybė sugebėti integruoti naujai atsirandančių žemėlapių grupes. / This dissertation provides an overall in-depth use evaluation methodology that assists in analysing of military aeronautical maps, sign system and records. On the basis of this research of signs and their conventions an optimised map and content of a unified Lithuanian military aeronautical database structures is suggested for improvement. Methodically prepared research was collected and based on already established and consistent thematic maps, signs and carto-semiotic assessment practices already used in Lithuania. A variety of illustrations and aspect assessments established an accurate and in-depth aeronautical value of signs and their practices. The analysis highlighted that not all carto-semiotic characters and signs of military aeronautical charts meet the criteria, and therefore could be changed. Previous military aeronautical sign analysis and their improvements were based on exercises of psycho-physiological studies of perception with their conclusions. Therefore a set of new aeronautical map characters that fully comply with psycho-physiological research recommendations are proposed. Through the examination of NATO's military aeronautical maps, charts and a look at a unified system of classifications, and its requirements, the dissertation summarises the overall work of the NATO’s military aeronautical maps and their classifications, which provides the possibility of integration for the newly emerging sign and map groups.
78

Karinių aeronavigacinių žemėlapių optimizavimas / Optimization of military airnavigation charts

Ovodas, Donatas 27 December 2012 (has links)
Disertaciniame darbe pasitelkiant kompleksinė vertinimo metodika analizuojami karinių aeronavigacinių žemėlapių ženklai, ženklų sistemos ir užrašai. Šios analizės pagrindu tobulinami sutartiniai ženklai, optimizuojamas žemėlapio turinys ir pateikiama vieningos Lietuvos karo aeronavigacinių duomenų bazės struktūrą. Kompleksiškai parengta tyrimo metodika rėmėsi Lietuvoje nusistovėjusia teminių žemėlapių ir ženklų kartosemiotine vertinimo praktika. Įvairūs ženklų ir užrašų vertinimo aspektai leido tiksliai ir nuodugniai atlikti aeronavigacinių ženklų ir užrašų vertinimą. Analizės metu nustatyta kad ne visi karinių aeronavigacinių žemėlapių ženklai atitinka kartosemiotikos reikalavimų, todėl galėtu būti keičiami. Karinių aeronavigacinių ženklų analizė ir tobulinimas rėmėsi ankščiau vykdytais psichofiziologinio suvokimo tyrimais bei išvadomis. Siūlomi nauji aeronavigacinių žemėlapių ženklai pilnai atitinka psichofiziologinių tyrimų rekomendacijas. Išnagrinėjus karinius NATO šalių aeronavigacinius žemėlapius ir atsižvelgiant į vieningą žemėlapių sistemą, klasifikacijos požymius ir atitinkamus klasifikacijų reikalavimus, darbe pateikta apibendrinta NATO šalių karinių aeronavigacinių žemėlapių klasifikacija, kurioje yra numatyta galimybė sugebėti integruoti naujai atsirandančių žemėlapių grupes. / This dissertation provides an overall in-depth use evaluation methodology that assists in analysing of military aeronautical maps, sign system and records. On the basis of this research of signs and their conventions an optimised map and content of a unified Lithuanian military aeronautical database structures is suggested for improvement. Methodically prepared research was collected and based on already established and consistent thematic maps, signs and carto-semiotic assessment practices already used in Lithuania. A variety of illustrations and aspect assessments established an accurate and in-depth aeronautical value of signs and their practices. The analysis highlighted that not all carto-semiotic characters and signs of military aeronautical charts meet the criteria, and therefore could be changed. Previous military aeronautical sign analysis and their improvements were based on exercises of psycho-physiological studies of perception with their conclusions. Therefore a set of new aeronautical map characters that fully comply with psycho-physiological research recommendations are proposed. Through the examination of NATO's military aeronautical maps, charts and a look at a unified system of classifications, and its requirements, the dissertation summarises the overall work of the NATO’s military aeronautical maps and their classifications, which provides the possibility of integration for the newly emerging sign and map groups.
79

Les dynamiques raciales dans la production de Michael Jackson (1979-2001) : aspects commerciaux, musicaux et visuels / Racial dynamics in Michael Jackson’s production (1979-2001) : marketing, musical and visual aspects

Petitjean, Isabelle 20 January 2018 (has links)
Notre thèse analyse la production artistique de Michael Jackson, en termes commerciaux, stylistiques, visuels, en ciblant les dynamiques et tensions raciales qui innervent ses strates narratives. La première partie porte sur les classements coloristes et la posture ubiquitaire des opus jacksoniens, recontextualisés au sein de la société américaine et de l’industrie du disque racialisée. La deuxième partie analyse les composantes éclectiques et stylistiques de la pop jacksonienne et la manière dont les conventions employées se situent et opèrent face aux constructions catégoristes existantes. Enfin, la troisième partie traite des dynamiques et tensions raciales portées par les productions visuelles (vidéos, image artistique) et les textes, comme autant de fondements identitaires de son potentiel crossover et fédérateur auprès d’un public international et transracial. / Our thesis analyses Michael Jackson’s artistic production, through marketing, stylistic and visual aspects, targeting racial dynamics and tensions which invigorate its narrative layers. The first part is about the colorist charts and the ubiquitous posture of jacksonian opuses, recontextualized against american society and racialized record industry. The second part analyzes the stylistic eclectism of Jackson’s pop music and the way he uses the conventions from the musical and racial categorization. Finally, the third part is about racial dynamics and tensions carried by visual productions (video clip, artistic image) and lyrics, as elements of identity fundations of Jackson’s crossover and his federative appeal to an international and transracial audience.
80

A utilizaÃÃo de objetos de aprendizagem para a compreensÃo e construÃÃo de grÃficos estatÃsticos. / Use of learning objects for understanding and construction of charts

Juscileide Braga de Castro 03 October 2012 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O tratamento da informaÃÃo à importante para a formaÃÃo do cidadÃo, pois estamos cercados de dados e fatos que precisam ser compreendidos. Contudo, avaliaÃÃes recentes do Sistema de AvaliaÃÃo da EducaÃÃo BÃsica (SAEB) e do Instituto Nacional de Alfabetismo Funcional (INAF) indicam as dificuldades de estudantes e atà de adultos das diversas regiÃes do paÃs, apresentam no entendimento da representaÃÃo de dados em grÃficos e em tabelas e em compreender os conceitos matemÃticos envolvidos. Pesquisas revelam que o estudo de grÃficos atravÃs de recursos tecnolÃgicos como computador e tecnologias digitais, favorece o desenvolvimento da aprendizagem de conceitos estatÃsticos, pois, na maioria das vezes, auxiliam a visualizaÃÃo e a exploraÃÃo de um conjunto de atividades, propiciando novas formas de pensar e agir. Dessa forma, realizou-se uma intervenÃÃo com um conjunto de atividades baseada no uso de objetos de aprendizagem (OA), a fim de verificar como o uso de tecnologias digitais contribui na aprendizagem de conceitos envolvidos no tratamento da informaÃÃo como construÃÃo e interpretaÃÃo de grÃficos de barras e de setores. A pesquisa foi realizada em uma escola pÃblica municipal de Fortaleza participante do Projeto Um Computador por Aluno - UCA, com duas turmas do 5 ano do Ensino Fundamental, com 26 alunos em cada uma. As turmas foram divididas em: Grupo Controle (GC) e Grupo Experimental (GE). A investigaÃÃo foi dividida em trÃs etapas: prÃ-teste, intervenÃÃo e pÃs-teste. Todos os alunos participaram do prÃ-teste e do pÃs-teste, aplicados individualmente e sem uso do computador. Todavia, ao GC nÃo foi ministrado nenhuma instruÃÃo formal alÃm da recebida em sala de aula. O GE foi submetido à intervenÃÃo que contemplou: aspectos matemÃticos de grÃficos e tabela, situaÃÃes-problema com classificaÃÃo e proporcionalidade e atividades de investigaÃÃo. Os dados foram analisados de modo a conhecer e compreender o desempenho dos alunos antes e apÃs as atividades, a evoluÃÃo de estratÃgias e o tratamento da informaÃÃo. Os estudantes que foram submetidos à intervenÃÃo apresentaram, estatisticamente, um desempenho superior quando comparado aos estudantes do GC. Constatou-se a evoluÃÃo das estratÃgias das crianÃas do GE, a partir de atividades desenvolvidas durante pesquisa. Essas atividades proporcionaram a integraÃÃo das diferentes tecnologias existentes na escola ao currÃculo escolar (laptop, tecnologias digitais e analÃgicas). Assim, o uso de tecnologias digitais permitiu a vivÃncia de experiÃncias didÃticas de tratamento da informaÃÃo das quais possibilitou: visualizar e simular diferentes situaÃÃes (representaÃÃo de grÃficos diferentes, de coleta e anÃlise de dados); tratar a informaÃÃo; trabalhar com situaÃÃes reais e com contextos investigativos e explorar os dados produzidos. Logo, os resultados deste estudo contribuem para melhor compreender a aprendizagem de grÃficos, assim como para o desenvolvimento de novos recursos e atividades. / The information processing is important for the citizen formation, since we are surrounded by data and facts that need to be understood. However, recent evaluations such as SAEB and INAF indicated the difficulties that children and adults from several Brazilian regions have been in the understanding of the processes related to data representation in graphs and tables, as well as understand involved mathematical concepts. Research have showed that the study of graphs by using of technological devices such as computer and another digital technologies, favoring the development of statistical concepts learning since these strategies help the visualization and exploration of many activities, providing new ways of thinking and act. Thus, the current study investigated as a didactic sequence, using learning objects (LO), could help in the understanding of concepts related to information processing as the construction and interpretation of bar and sectors graphs. The work was conducted in a Brazilian public school located in Fortaleza city using two classes of 5th grade of elementary school, with 26 students each ones. The school classes were divided in control group (CG) and experimental group (EG) and all students were previously evaluated through a pre-test. Posteriorly an intervention using a didactic sequence including mathematical aspects of graphs and tables, problem situations with classification and proportionality and research activities was performed only with EG. The GC was not exposed to any formal education beyond the classroom received. Thereafter a post test was applied to both groups (CG and EG). The data were analyzed by student performance before and after the performed activities taking into account the evolution of strategies and information processing. Was observed a improviment in the strategies used by children for GE group after intervention. These activities give the integration of different technologies employed in school curriculum (laptop and digital and analogic technologies). Thus, the use of digital technologies provided didatic experiences in processing information by students as a to visualize and simulate different situations; process information; work with real situations, with investigative contexts and explore the produced data. Therefore, the results of current study contribute to better understand the graphs learning as well as for further development of new resources and activities.

Page generated in 0.0391 seconds