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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Combined Digital Holography and Speckle Correlation for Rapid Shape Evaluation

Khodadad, Davood January 2014 (has links)
In manufacturing industry there is a high demand for on line quality control to minimize the risk of incorrectly produced objects. Conventional contact measurement methods are usually slow and invasive, meaning that they cannot be used for soft materials and for complex shapes without influencing thecontrolled parts. In contrast, interferometry and digital holography in combination with computers become faster, more reliable and highly accurate as an alternative non-contact technique for industrial shape evaluation. In digital holography, access to the complex wave field and the possibility tonumerically reconstruct holograms in different planes introduce a new degree of flexibility to optical metrology. With digital holography high resolution and precise three dimensional (3D) images of the manufactured parts can be generated. This technique can also be used to capture data in a single exposure,which is important when doing measurements in a disturbed environment.The aim of this thesis is to perform online process control of free-form manufactured objects by measuring the shape and compare it to the CAD-model. To do this, a new technique to measure surface gradients and shape based on single-shot dual wavelength digital holography and image correlation of speckle displacements is demonstrated. Based on an analytical relation between phase gradients and speckle displacements it is shown that an object is retrieved uniquely to shape and position without the unwrapping problems that usually appear in dual wavelength holography. The method is firstdemonstrated using continues wave laser light from two temperature controlled laser diodes operating at 640 nm. Further a specially designed dual core diode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm is used. One significant problem when using the dual wavelength single-shot approach is that phase ambiguities are built in to the system that needs to be corrected. An automatic calibration scheme is therefore required. The intrinsic flexibility of digital holography gives a possibility to compensate these aberrations and to remove errors, fully numerically without mechanical movements. In this thesis I present a calibration method which allows single-shot online shape evaluation in a disturbed environment. It is shown that phase maps and speckle displacements can be recovered free of chromatic aberrations. This is the first time that a single-shot dual wavelength calibration is reported by defining a criteria to make an automatic procedure.By the results of the presented work, it is experimentally verified that the single-shot dual wavelength digital holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve and evaluate the object shape. The proposed method is also robust to large phasegradients and large movements within the intensity patterns. The advantage of the approach is that, using speckle displacements, the shape measurement can be done even though the synthetic wavelength is out of the dynamic range of the height variation of the object.

Applications of the PEXE-concept for maintenance policies and proportional hazards models

Westberg, Ulf January 1994 (has links)
No description available.

Process capability studies in theory and practice

Deleryd, Mats January 1996 (has links)
The existence of variation has been a major problem within industry since the early days of the industrial revolution and perhaps even earlier. The fact that two parts not ever will be identical, forces every organisation to find a strategy for how to master variation. Process capability studies, a method designed to judge whether a process is capable or not, often plays an important part in such a strategy.The concept of process capability studies has received both positive and negative criticism during the last decade. For instance, the supporters of process capability studies emphasise the importance of using the method to identify improvement priorities to be focused in the overall improvement process within an organisation.However, as all methods, process capability studies has its limitations. Actually, it is not principally the method as such that has been criticised, but rather the measures of capability used when conducting process capability studies, the so called process capability indices. All existing process capability indices have some weaknesses, even the most sophisticated indices have relatively poor statistical properties which might lead the user to make incorrect decisions, even if most theoretical aspects of how to conduct process capability studies are known by the user. The use of process capability indices is for instance partly based on the assumption that the process output is normally distributed, a condition that is often not fulfilled in practice, where it is common that the process output is more or less skewed.This thesis focuses on process capability studies in both theory and practice. In part 1 of the thesis some theoretical aspects of how to conduct process capability studies are identified and then the adherence to these aspects within Swedish industry is investigated. This study reveals that there are certain gaps between how process capability studies are supposed to be conducted according to theory and the way they actually are carried out in practice. The study also tries to explain why these gaps exist, by analysing common obstacles when implementing and conducting process capability studies.In part 2, a simulation study focusing on the effects of skewness on estimates of some process capability indices belonging to the family of indices named Cis presented. The effects of skewness are studied in three different cases, one incapable case, one case just capable and one very capable case. In all cases, four lognormal distributions with different skewness are used. The results from the simulation study indicate that the effect of skewness is relatively systematic, and therefore there are some hope that future investigations might use these results when formulating some practical solution to the problem of how to use process capability indices when the process monitored has a skewly distributed output.Finally, the results are summarised and discussed and some suggestions for future research are given.

Reliability-centred maintenance : identification of management and organisational aspects when introducing RCM

Backlund, Fredrik January 1999 (has links)
Increased demands on productivity, quality and cost-efficiency affecting manufacturing trends towards increased complexity and higher degree of process automation. A major break down in such a manufacturing system may generate severe damage on productivity, environment and personnel. Using risk assessment to identify serve risks within a plant, in combination with different maintenance strategies, is one course of action to prioritising maintenance activities needed. A methodology for executing a so-called risk-based maintenance is reliability-centred maintenance, RCM. There are several benefits generated from RCM, for example, improved safety and maintenance cost-effectiveness. Though, several companies have problems to make it work. The problems that occur are many times within management and organisational (M&amp;O) aspects, such as lack of communication and management support. Some M&amp;O aspects of importance when introducing improvement methods as TQM and TPM are similar with the ones valid for RCM. Though, differences seem to depend on the use of RCM in a more technology environment, overshadow the affects M&amp;O aspects really bring about when introducing it. That is probably the main reason why obstacles occur when introducing RCM. A structured step model has been developed, focusing on the preparation and planning activities when introducing RCM. / <p>Godkänd; 1999; 20070403 (ysko)</p>

Quality management for sustainable health: methodologies, values and practices taken from Swedish organizations

Bäckström, Ingela January 2006 (has links)
In many Western countries today, not least in Sweden, there are a lot of organizations that have great problems with sickness absence. The costs connected to the high rates of sickness absence have also risen to alarming levels. Healthy co-workers and healthy organizations are obvious goals for many leaders, but this is not always so easy to establish. Work practices and leadership that are beneficial to co-worker health are thus vital to identify. Studies have shown relationships between company-wide implementation of quality programs and improved co-worker satisfaction along with low co-worker turn over; in other words, co-worker health along with improved customer satisfaction and financial results. Despite the great problems concerning sickness absence, there are organizations that have been awarded prizes for excellence in leadership, internal partnership, working environment, and profitability. The overall purposes of the research described in this thesis are to examine and describe how management and leadership can establish sustainable health among the co-workers and examine how the leadership for sustainable health is related to Quality Management. The in-depth purpose is to examine which aspects within the values derived from the quality movement are those that primarily influence the co-workers' perceived health. The results presented can be described in three parts and are results from four case studies carried out in five different organizations. Three of the organizations have received awards for establishing good working environment, good financial results, and low sick leaves among their co- workers; the fourth received an award for the successful implementation of quality programs. The first part consists of results from case studies in three different organizations and describes how organizations can work to achieve sustainable health among their co-workers, with practical examples. The results are methodologies, values and organizational structure, which it is considered possible for other organizations to adopt in their efforts to achieve good working conditions resulting in fewer sick leaves. The second part is an attempt to investigate if leadership for sustainable health is related to Quality Management. Methodologies, leadership values, organizational structure, and general values found in organizations which have achieved sustainable health are analyzed in the light of Deming's 14 points, and a correlation is indicated. There is also correlation found between the TQM values and the co-workers' perception of their health. The third part examines which of the aspects within the values grown from the quality movement are those that influence the co-workers perceived health. The results show significant correlation between the values and the co-workers' perception of their health. Aspects found within the value "Top management commitment" were named; Empathy, Presence and Communication, Integrity, and Continuity. Within the value "Let everybody be committed" the aspects; Development, Influence and Being informed were found. These aspects are described in more detail and also in one model per value. The result implies that the TQM values; "Top management commitment", "Improve continuously" "Let everybody be Committed" and "Focus on customers" are important for achieving healthy organizations and sustainable health among co-workers. / <p>Godkänd; 2006; 20061206 (pafi)</p>

Contributions to the use of designed experiments in continuous processes : a study of blast furnace experiments

Vanhatalo, Erik January 2007 (has links)
Design of Experiments (DoE) contains techniques, such as factorial designs, that help experimenters maximize the information output from conducted experiments and minimize the amount of experimental work required to reach statistically significant results. The use of DoE in industrial processes is frequently and thoroughly described in literature. However, continuous processes in industry, frequently found in, for example, the mining and steel industries, highlight special issues that are typically not addressed in the DoE literature. The purpose of this research is to contribute to an increased knowledge of the use of DoE in continuous processes and aims to investigate if factorial designs and other existing techniques in the DoE field are effective tools also in continuous processes. Two studies have been performed. The focus of the first study, a case study of an industrial blast furnace operation, is to explore the potential of using factorial designs in a continuous process and to develop an effective analysis procedure for the experiments in a continuous process. The first study includes, for example, interviews, experiments, and large elements of action research. The focus of the second study is to explore how a-priori process knowledge can be used to increase the analysis sensitivity for unreplicated experiments. The second study includes a metastudy of experiments in literature as well as an experiment. The results show that it is possible to use factorial designs in a continuous process even though it is not straightforward and special considerations by the experimenter will be required. For example, the dynamic nature of continuous processes affects the minimum time required for each run in an experiment since a transient time period is needed between each run to allow the experimental treatments to reach full effect in the process. Therefore, the use of split-plot designs is recommended since it can be hard to completely randomize the experimental run order. It is also found that process control, during the conduction of the experiment, may be unavoidable in continuous processes. Thus, developing a process control strategy during the planning phase is found to be an important experimental success factor. Furthermore, the results indicate that the multitude of cross-correlated response variables typical for continuous processes can be problematic during the planning phase of the experiment. The many and cross-correlated response variables are also reasons to why multivariate statistical techniques, such as principal component analysis, can make an important contribution during the analysis. Moreover, a-priori process knowledge is confirmed to have a positive effect on analysis sensitivity for unreplicated experiments. Since experimental effects in continuous processes can be expected to be small compared to noise, a-priori process knowledge can also make a valuable contribution during analysis of experiments in continuous processes. Furthermore, activities like coordination of people, information and communication as well as logistics planning are found as important parts of the experimental effort in continuous processes. / Försöksplanering innehåller metoder och verktyg, exempelvis faktorförsök, som hjälper den som utför experiment att maximera informationsutbytet från experimenten och samtidigt minimera mängden resurser som krävs för att nå statistiskt säkerställda resultat. Användandet av försöksplanering i industriella processer beskrivs ofta och utförligt i litteraturen, men kontinuerliga tillverkningsprocesser, som ofta hittas i exempelvis gruv- och stålindustrin, medför en problematik som normalt inte beskrivs i försöksplaneringslitteratur. Syftet med forskningen i denna avhandling är att bidra till en ökad kunskap om användandet av försöksplanering i kontinuerliga processer genom att undersöka om faktorförsök och andra verktyg inom försöksplaneringsområdet är effektiva också i kontinuerliga processer. För att uppnå syftet genomfördes två studier. Den första studien är en fallstudie vid en industriell masugnsanläggning. Här utreds, genom intervjuer, experiment och aktionsforskning, potentialen i att använda faktorförsök i en kontinuerlig process och en analysmetodik för experiment i kontinuerliga processer utvecklas. Den andra studien undersöker, genom en metastudie av experiment från litteratur samt ett experiment, hur a-priori processkunskap kan användas för att öka känsligheten i analys av icke upprepade experiment. Resultaten visar att det är möjligt att använda faktorförsök i en kontinuerlig process men att det kräver speciella överväganden av försöksplaneraren. Exempelvis påverkar den dynamiska karaktären hos kontinuerliga processer den minsta möjliga tid som krävs för varje delförsök eftersom en omställningstid, mellan varje delförsök, behövs för att de förändringar som görs ska nå full effekt i processen. Det kan därför vara svårt att använda en fullständigt randomiserad försöksording. Istället rekommenderas användningen av så kallade split-plot-försök där begränsningar i randomiseringsordningen görs. Vidare är processtyrning ofta oundvikligt samtidigt som experimenten pågår, vilket gör det viktigt att i förväg formulera en styrstrategi för att minimera styrningens påverkan på försöksresultaten. Resultaten visar också att den stora mängden korskorrelerade resultatvariabler, som är vanliga i kontinuerliga processer, kan skapa problem under planeringen av experimenten. De många och korskorrelerade resultatvariablerna är också en orsak till att multivariata statistiska verktyg, som t.ex. principalkomponentanalys, kan vara värdefulla hjälpmedel under analysen. Vidare visar resultaten att nyttjandet av a-priori processkunskap under analysen har en positiv effekt på analysresultaten för icke upprepade försök. Eftersom effekter av förändringar i kontinuerliga processer ofta förväntas vara små jämfört med brus kan a-priori processkunskap ge ett värdefullt bidrag vid analys av experiment i kontinuerliga processer. Resultaten visar också på vikten av exempelvis koordination av personal, information, kommunikation och logistikplanering för att lyckas bra med ett experiment i en kontinuerlig process. / <p>ISRN: LTU-LIC--07/66--SE</p>

En arbetsmodell för intervallplanerat underhåll : Planering och kostnadsberäkning för underhållsarbete

Lind, Elias, Västerbo, Erik January 2021 (has links)
Denna studie har genomförts hos en uppdragsgivare som verkar inom livsmedelsindustrin. Studien genomfördes då en av deras maskiner i produktionslinan har återkommande haverier. Maskinen är det sista steget i paketeringen och kallas för tejpnedtryckare. Den fäster en tejpremsa på förpackningarna för att försegla förpackningen under tillverkningsprocessen samt att konsumenterna kan återförsegla förpackningen vid användning. Maskinens oplanerade stopptid står för 2,4 procent av den totala produktionstiden och ett genomsnittligt avhjälpande underhållsarbete på tejpnedtryckaren tar två timmar. När studien genomfördes fanns det ingen tydlig plan för hur förebyggande underhåll på maskinen skulle utföras för att minska de haverier som inträffar. Syftet med denna studie är att minska den stopptid som uppstår på grund av haverier vid tejpnedtryckaren och målet med denna studie är därför att presentera en arbetsmodell för planering och kostnadsberäkningar av underhållsarbete. För att uppfylla studiens mål och syfte användes olika metoder. Det första som gjordes var att samla in data med hjälp av observationer, intervjuer och uppdragsgivarens databas. Utifrån datainsamlingen skapades det sedan ett Ishikawadiagram som visade vilka felkällor det finns till haverierna. Efter det utfördes en parvis jämförelse mellan felkällorna för att rangordna felen i hur allvarlig konsekvensen av ett haveri är. För att validera rangordningen av felkällorna gjordes en FMEA vid sidan av Ishikawadiagrammet. Efter felkällorna rangordnats beräknades dessa i en Weibullmodell för att få ut ett intervall för förebyggande underhåll. För att se underhållsarbetet ur ett ekonomiskt perspektiv utfördes beräkningar för att se vilken typ av underhållsarbete som ska utföras. Metoderna sammanfattades till en arbetsmodell som kan användas för att utreda och implementera underhåll på utrustning som saknar tillståndsbaserad övervakning. Arbetsmodellen består av en instruktion för hur modellen ska användas och kalkylark för kostnads- och intervallberäkningar. Stegen i modellen är genomförda i denna studie för att säkerställa att det är genomförbart och att det går att applicera på en maskin utan tillståndsbaserad övervakning. Felkällornas haveridatum var tvetydiga då underhållsrapporterna från uppdragsgivaren var mycket bristfälliga och svåra att tyda. Det var inte alltid möjligt att utläsa hur eller vad underhållet var utfört på. Detta medför att trovärdigheten för Ishikawadiagrammets, FMEA:ns och intervallberäkningarnas resultat är låg. FMEA, Ishikawadiagrammet och parvis jämförelse ingår inte i den slutgiltiga arbetsmodellen då de var överflödiga.

Kundperspektivet vid Barnahus : En fallstudie om återkoppling till barn i brottsutredningar

Ravald, Emma January 2020 (has links)
Vid Barnahus utreds brott där barn misstänks ha blivit utsatta för övergrepp. Barnahus-tanken är samla och samordna aktörer från olika myndigheter under ett och samma tak så att barnet ska slippa att bollas runt mellan myndigheter. Barnet ska skyddas i rättsprocessen genom att brottsutredningsprocessen anpassas till barnet. Tidigare utvärderingar har visat att Barnahus förbättrar bemötandet av barnet, men det har inte visat på bättre resultat för brottsutredningarna, det vill säga att fler brott klaras upp. Det har också framkommit att det finns brister i information till barn och att barn inte får återkoppling om att en brottsutredning som de har varit en del av har lagts ned.Syftet med uppsatsen är att undersöka hur kundperspektivet syns i brottsutredningsprocessen för att kunna förbättra rutinerna för återkoppling till barn.En kvalitativ studie har genomförts genom att intervjua olika kategorier av yrkesverksamma vid ett specifikt Barnahus. Empirin har analyserats utifrån ett kundperspektiv med hjälp av sju framtagna kriterier för kundorientering.Resultatet visar att det saknas rutiner kring återkoppling till barn om att en brottsutredning har lagts ned och att det intervjuade har olika uppfattning om hur den i praktiken sker. Barn riskerar att inte få någon återkoppling alls, särskilt små barn. Riktlinjer och rutiner behöver förbättras och återkopplingen bättre anpassas efter barnens individuella förutsättningar. Kundperspektivet syns i början av brottsutredningsprocessen, inför och vid förhöret med barnet. I slutet av processen är det mindre synligt. Det är också i den delen av processen där återkopplingen till barn förväntas ske. Studiens resultat kan bidra till en ökad kundorientering vid det undersökta Barnahuset, men även användas vid andra Barnahus. / At Barnahus investigations about child abuse are being conducted. The idea of Barnahus is to gather and coordinate actors from different authorities under the same roof so that children will not be passed around between the authorities. With crime investigations adopted to the child, the child should be protected within the justice process. Earlier evaluations have shown that because of Barnahus the treatment of the child is better than before, but the crime investigations do not show better results, namely more crimes are not being solved. Lack of information has also emerged and that children sometimes do not get feedback about a disused investigation concerning them.The purpose of this essay is to investigate how customer orientation is visible in the crime investigation process in order to improve the routines for feedback to children.A qualitative study has been conducted through interviews with different categories of professional actors at a specific Barnahus. The empirical findings have been analysed from a customer perspective with the support of seven different criterion for customer orientation.The results show that there is a lack of routines for feedback to give children about disused crime investigation and that the interviewees have different views about how feedback in practice is conducted. Children risk not to get any feedback; this is especially so for younger children. Guidelines and routines need to improve and feedback need to be better adapted to individual conditions. The customer perspective is visible in the beginning of the crime investigation process, before and during the hearing with the child. In the end of the process it is less visible. It is the same part of the process where feedback to the child is expected to be conducted. The result of the study can contribute to increased customer orientation at the Barnahus that is subject for the study, but also to Barnahus in general. / <p>2020-06-26</p>

Strävar ni efter bättre idéer och ökadmotivation till förbättringsarbetet : Då kan en medarbetardriven processkartläggning vara det rättaverktyget för er!

Sebaa, Nadine January 2020 (has links)
Syftet med denna studie var att öka förståelsen för hur en"Medarbetardriven processkartläggning" skulle kunna användas som ettverktyg i förbättringsarbete genom att stimulera till fler förbättringsförslagsamt öka motivationen till förbättringsarbete. Utgångspunkt för studienhar grundats i författarens intresse för processkartor samt antagandet omatt en processkartläggning inte genomförs av medarbetarna iorganisationen utan av människor med kompetens om hur enprocesskartläggning går till.För att besvara studiens syfte användes en experimentell studiedesignsom inkluderade åtta studiedeltagarna som delades upp i två grupper,Grupp A och Grupp B. Innan studien startade fick studiedeltagarna skattasin egen motivation till förbättringsförslag och förbättringsarbete genomen enkät. Studiedeltagarna i Grupp A genomförde sedan en"Medarbetardriven processkartläggning" och Grupp B fick göra en"Analys av en skapad processkarta". Under tiden som studiedeltagarnagenomförde uppgiften uppmanades de att tänka ut nyaförbättringsförslag. Efter studien fick studiedeltagarna åter besvaraenkäten som utvärderade motivationen, detta för att se om motivationenpåverkats efter studien. Resultatet visade att en Medarbetardrivenprocesskartläggning ökade motivationen till förbättringsarbete samtgenererar i fler-, bättre och mer kreativa förbättringsförslag, detta ijämförelse med en "Analys av en processkarta". / The purpose of this study was to increase the understanding of how an"Employee-driven process mapping" could be used as a tool inimprovement work by stimulating more improvement suggestions andincreasing motivation for improvement work. The study was based on theauthor's interest in process mapping and the assumption that a processmapping is not carried out by the employees in the organization but bypeople with skills in how a process mapping is done.To answer the purpose of the study, an experimental study design wasused that included eight study participants who were divided into twogroups, Group A and Group B. Before the study started, the studyparticipants had to estimate their own motivation for improvementproposals and improvement work through a questionnaire. The studyparticipants in Group A then completed an "Employee-driven processmapping" and Group B had to do an "Analysis of a created process map".As the study participants completed the task, they were invited to devisenew improvement proposals. After the study, the study participants wereagain asked to answer the questionnaire that evaluated the motivation,to see if the motivation was affected after the study. The result showedthat an Employee-driven process mapping increased the motivation forimprovement work and generates in more, better and more creativeimprovement proposals, this in comparison with an "Analysis of a processmap". / <p>2020-06-26</p>

Process improvement in a third world organisation : a study from Sub Saharan Africa

Isaksson, Raine January 2001 (has links)
First World improvement theory has been tested in a Third World organisation. A First World improvement process has been defined as a tool for testing. The objective of this thesis is to answer the research question: How does a Third World environment influence the introduction and application of a First World improvement process? The proposed five-stage improvement process was applied in case studies, which examined the Companywide Process, Cement Packing and Quality Control. The conclusion is that a First World improvement process, with only minor changes, can operate successfully in a Third World environment, provided management is truly committed to the concept of improvement. / <p>Godkänd; 2001; 20070314 (ysko)</p>

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