• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 147
  • 138
  • 50
  • 38
  • 8
  • 6
  • 5
  • 5
  • 4
  • 4
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 480
  • 121
  • 41
  • 39
  • 38
  • 35
  • 34
  • 30
  • 29
  • 28
  • 26
  • 25
  • 24
  • 23
  • 23
  • 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.
171

Análise tempo-freqüência de regimes de escoamento bifásico gás-líquido intermitentes em tubo horizontal / Time-frequency analysis of intermittent two-phase flows in horizontal piping

Fabiana Lopes Klein 20 October 2004 (has links)
Um dos atributos fundamentais associados aos escoamentos multifásicos é a existência de estruturas características segundo as quais as diferentes fases do líquido escoam. O surgimento de uma dessas estruturas, conhecidas como configurações ou regimes de escoamento, é determinado pelas vazões e propriedades físicas dos componentes, além de parâmetros geométricos como diâmetro e inclinação do conduto. O desenvolvimento de metodologias de caracterização de regimes, bem como a caracterização e o diagnóstico da transição destes regimes de escoamento são de fundamental importância. Este trabalho utiliza a análise tempo-frequência da transformada de Gabor para caracterizar os regimes de escoamento horizontais gás-líquido intermitentes. Mais especificamente, o principal objetivo está em investigar a existência de sub-regimes dentro do regime intermitente, para tanto recorremos à covariância tempo-frequência da transformada de Gabor, que é capaz de detectar transições através da não-estacionaridade associada com as correspondentes transições. Testes experimentais foram conduzidos no circuito TALC em CEA-Grenoble e uma extensiva base de dados foi obtida, cobrindo diversos tipos de escoamento intermitente. Uma sonda de condutividade elétrica, consistindo de dois anéis de eletrodos montados junto à tubulação, produziu sinais dos quais a covariância tempo-frequência foi calculada através da correspondente transformada de Gabor. / One of the main features associated to multiphase flows is the existence of characteristic dynamic structures according to which the different phases of a mixture of immiscible fluids can flow. The manifestation of one of these structures, known a flow pattern or regime, is determined by the flow rates as well as by physical and geometrical properties of the fluids and piping. The development of flow pattern characterization and diagnostic methods, and the associated transitions in between, is of crucial importance for an efficient engineering of such phenomena. Time-frequency analysis based on the Gabor transform is used in this work to characterize horizontal air-water intermittent flow regimes. More specifically, our main objective is to reveal the existence of sub-regimes inside the intermittent regimes region with the help of the corresponding time-frequency covariance based on the Gabor transform, which is capable of detecting transitions by assessing the unstationarity associated with the corresponding transitions. Experimental tests were conducted at the TALC facility at CEA-Grenoble and an extensive database was obtained, covering several types of intermittent flow. A conductivity probe, consisting in two ring electrodes flush mounted to the pipe, delivered signals from which the time-frequency covariance were calculated from the corresponding Gabor transform.
172

Jämförelse av två olika fälttest för fotbollsspelare på olika tävlingsnivåer

Althage, Stefan, Lundberg, Peter January 2010 (has links)
Sammanfattning Olika fälttest är flitigt använda för att utvärdera fotbollsspelares fysiska uthållighet, däribland Yo-Yo Intermittent Recovery Level 1 (Yo-Yo IR1) och Coopers löptest. Ytterst lite är dock känt om Coopertestets lämplighet som mätmetod i en sport med intermittent arbete som fotboll. Syftet med denna studie var att undersöka prestation i Coopertestet i förhållande till Yo-Yo IR1 testet hos fotbollsspelare på olika tävlingsnivåer. Under försäsongen testades 19 manliga fotbollsspelare (23 ± 4 år, 181 ± 9 cm, 77 ± 9 kg) från svensk division 1 (hög-nivå, n=5), division 3 (mellan-nivå, n=6) och division 5 (låg-nivå, n=8). Coopertestet består av oavbruten löpning så långt som möjligt under 12 minuter på löparbana. Yo-Yo IR1 testet består av upprepade 2x20 meters löpningar i ökande hastighet, med 10 sekunder aktiv vila mellan varje omgång. Testerna utfördes under standardiserade former på kvällstid med minst 72 timmars mellanrum. Resultatet för Coopertestet var; hög-nivå 3056 ± 194m, mellan-nivå 2950 ± 188m och låg-nivå 2916 ± 203m, utan signifikanta skillnader mellan grupperna (p>0,05). Yo-Yo IR1 resultaten var; hög-nivå 2264 ± 286m, mellan-nivå 1933 ± 395m och låg-nivå 1615 ± 496m. Det fanns en signifikant skillnad i testresultaten mellan hög-nivå och låg-nivå (p<0,05). Förhållandet mellan de två testerna för hela populationen var r=0,89 (p<0,001), och inom grupperna; hög-nivå r=0,69 (p=0,2), mellan-nivå r=0,99 (p<0,001) och låg-nivå r=0,98 (p<0,001). I motsats till övriga grupper visade resultaten att hög-nivå gruppen, som har större mängd fotbollsspecifik träning, inte hade något signifikant samband mellan de två testen. Coopertestets utformning med oavbruten löpning, tillsammans med dess oförmåga att särskilja mellan olika tävlingsnivåer, medför att Yo-Yo IR1 testet bör användas framför Coopertestet i syfte att få tydligare information om en fotbollsspelares fysiska uthållighet under matchsituation.
173

The physiological impact of soccer on elite female players and the effects of active recovery training

Andersson, Helena M. January 2010 (has links)
Female soccer is becoming more popular and professional in the world. There are, however, limited scientific data available on how elite female players respond to physical stress during soccer games. An effective recovery strategy following a game is important, because there are few recovery days between the games in international tournaments. The present thesis, which was designed to mirror a competitive situation, aimed to investigate changes in several physiological systems occurring in female elite players in response to two soccer games. It also aimed to investigate the effects of active recovery training on the recovery of several physiological systems. METHODS: Two elite female soccer teams played two 90-min games separated by 72 h active or passive recovery. The active recovery training (cycling at 60% HRpeak, resistance training at <50% 1RM) lasted one hour and was performed 22 and 46 h after the first game. Countermovement jump (CMJ), 20-m sprint time and isokinetic knee strength were measured before, immediately, 5, 21, 45, 51, and 69 h after the first game, and immediately after the second game. The physical stress markers (CK, urea), oxidative stress markers (e.g., GSSG, lipid peroxidation), endogenous (e.g., UA, thiols) and dietary antioxidants (e.g., tocopherols, carotenoids) and a large battery of cytokines (e.g., IL-6, TNF-α) were analysed in blood. RESULTS: No significant differences were observed in the performance parameters, oxidative stress and antioxidant levels or inflammatory response between the active and passive recovery groups. Sprint and isokinetic knee strength were reduced by the same extent after both games. CMJ decreased after the first game and remained reduced throughout the study period. Blood physical stress markers, GSSG and endogenous antioxidants increased with similar amplitude after both games together with unchanged lipid peroxidation. The dietary antioxidants showed either a rapid and persistent change (e.g., tocopherols) or a delayed rise (carotenoids) after the first game. A transient increase occurred in several pro- (e.g., IL-12, TNF-a, MCP-1), anti-inflammatory (e.g., IL-4, IL-10, INF-a) and mixed (IL-6) cytokines after the first game. Fewer cytokines increased in response to the second game. CONCLUSION: Two repeated elite female soccer games separated by 72 h induced similar acute changes in several physiological parameters. After the first game, differences in the recovery pattern of the neuromuscular parameters occurred. In particular, the slow recovery of CMJ indicates that special attention should be devoted to the training of explosive force. Furthermore, the recruitment of antioxidants in response to the transient increase in GSSG resulted in the maintenance of the redox-balance in female players. Similarly, a strong and balanced pro- and anti-inflammatory cytokine response occurred after one single female soccer game. The consequences of the dampened cytokine response during repeated soccer games are, however, unknown. In general, the majority of the parameters had recovered prior to the second game and the physiological alterations induced by the first game did not affect the performance of players in the second game. Finally, active recovery training conducted after a soccer game does not accelerate the recovery time for neuromuscular, oxidative stress, antioxidant and inflammatory responses in elite female players.
174

The effects of casualization on the working conditions of temporary employees in the hospitality industry

Kuipers, Aiko 26 August 2015 (has links)
M.Tech. / Employees in the events management and conferencing sectors in the tourism and hospitality industries are employed on either full-time and or temporary working arrangements, referred to as casualization. Traditionally, a full complement of employees would be present at hospitality venues; however, economic conditions, occupancy levels and consequently turnover, have dramatically changed, leading to venues only employing staff when they are needed. A South African survey (2010) reveals that most temporary employees are contracted from labour brokers, who in turn sell their skills and services to the events management and conferencing sectors, among others in the hospitality industry. This change was necessary to enable employers to only employ staff for busy periods. (Hickmore, 2011; Mosala, 2008)...
175

Influência do estado de treinamento sobre o desempenho físico em resposta à suplementação de beta-alanina / Influence of training status on physical performance in response to beta-alanine supplementation

Vitor de Salles Painelli 29 April 2013 (has links)
Estudos recentes têm demonstrado que a suplementação de beta-alanina (BA) pode melhorar o desempenho físico. O mecanismo proposto para tal resultado envolve o aumento das concentrações intramusculares de carnosina, um dipeptídeo cuja função mais bem atribuída é a de manutenção do equilíbrio ácido-básico. Apesar do emergente corpo literário acerca dos efeitos ergogênicos da suplementação de BA, a maior parte das evidências provém de estudos conduzidos com indivíduos não treinados ou fisicamente ativos, enquanto os estudos com indivíduos treinados são escassos, e seus resultados, controversos. Tem sido especulado que a diferença na capacidade tamponante muscular entre indivíduos treinados e não treinados é um possível fator mascarando o efeito ergogênico da suplementação de BA em indivíduos treinados, já que têm sido demonstrado que este perfil de indivíduos possui maior capacidade tamponante e conteúdo muscular de carnosina. Assim, o objetivo do presente estudo foi investigar a influência do estado de treinamento sobre o desempenho físico intermitente de membros inferiores em resposta à suplementação de BA. Para tanto, 40 homens jovens e saudáveis foram recrutados para participar do estudo, e divididos em dois grupos de acordo com o seu estado de treinamento [ciclistas treinados (T) ou indivíduos não treinados (NT)]. Os participantes foram aleatoriamente designados a um grupo suplementado com BA ou placebo (dextrose - PL), provendo quatro condições experimentais: NTPL, NTBA, TPL e TBA. A suplementação foi realizada com a ingestão de 6.4 gramas de BA ou PL por dia, durante 4 semanas. Antes e após o período de suplementação, os participantes completaram 4 séries do teste de Wingate para membro inferior, com 30 segundos de duração cada uma e 3 minutos de descanso entre elas. O trabalho total realizado foi significantemente aumentado após o período de suplementação em ambos os grupos NTBA (+1349 ± 1411 kJ; P = 0.03) e TBA (+1978 ± 1508 kJ; P = 0.002), foi significantemente reduzido no grupo NTPL (-1385 ± 2815 kJ; P = 0.03), e não se alterou no grupo TPL (-219 ± 1507 kJ; P = 0.73). Comparada ao período pré-suplementação, a potência média no período pós-suplementação foi significantemente maior na série 4 para o grupo NTBA (P = 0.0004), enquanto a mesma foi maior nas séries 1, 2 e 4 (P <= 0.05) para o grupo TBA. Não foram observadas diferenças na potência média entre o período pré- e pós-suplementação para os grupos NTPL e TPL. Em conclusão, quatro semanas de suplementação de BA foram efetivas em melhorar o desempenho físico intermitente de membros inferiores em ambos os participantes treinados e não treinados. Estes dados ressaltam a eficácia ergogênica da suplementação de BA para exercícios de alta-intensidade, independentemente do estado de treinamento do indivíduo / Recent studies have demonstrated that beta-alanine (BA) supplementation can improve performance. The proposed mechanisms for this result involve an increased muscle carnosine content, a dipeptide whose function is attributed to the maintenance of acid-base balance. Even though the body of evidence surrounding the ergogenic effects of BA supplementation is increasing, most of the evidences come from studies conducted with physically active or untrained individuals, while studies with trained participants are scarce, and their results, controversial. It has been speculated that the difference in muscle buffering capacity between trained and untrained individuals is a possible factor masking the ergogenic effect of BA supplementation in trained individuals, who have already been demonstrated to have greater buffering capacity and muscle carnosine content. Therefore, the aim of this study was to investigate the influence of training status on intermittent lower-body performance in response to BA supplementation. For this purpose, forty young males were divided into two groups according to their training status (trained - T, and untrained - NT cyclists). Participants were further randomly allocated to BA or placebo (dextrose - PL) groups, providing four experimental conditions: NTPL, NTBA, TPL, TBA. BA or PL was ingested by 6.4 g·d-1, during for 4 weeks. Before and after the supplementation period, participants completed four 30-seconds lower-body Wingate bouts, separated by 3 minutes. Total work done was significantly increased following supplementation in both NTBA (+1349 ± 1411 kJ; P = 0.03) and TBA (+1978 ± 1508 kJ; P = 0.002), and it was significantly reduced in NTPL (-1385 ± 2815 kJ; P = 0.03) with no difference for TPL (-219 ± 1507 kJ; P = 0.73). Compared to pre-supplementation, post-supplementation mean power output was significantly higher in bout 4 for NTBA (P = 0.0004), and higher in bouts 1, 2 and 4 (P <= 0.05) for TBA. No differences were observed in mean power output for NTPL and TPL from pre- to post-supplementation period. In conclusion, four weeks of BA supplementation was effective at improving intermittent lower-body performance in both untrained and trained individuals. These data highlight the efficacy of BA as an ergogenic aid for high-intensity exercise regardless of the training status of the individual
176

Impact vasculaire et métabolique de l'hypoxie intermittente et de l'obésité dans un modèle murin / Vascular and metabolic impact of short-term intermittent hypoxia and obesity in mice

Trzepizur, Wojciech 15 December 2014 (has links)
L’augmentation constante de l’obésité dans les populations occidentales accroit la prévalence de nombreuses maladies liées au surpoids parmi lesquelles le syndrome d’apnées hypopnées du sommeil (SAHOS). Le SAHOS et l’obésité représentent deux facteurs de risque indépendants du développement de maladie cardiovasculaires (CV) et métaboliques. Etant souvent associés en pratique clinique, l’étude de leurs effets vasculaires et métaboliques spécifiques est difficile. Pour nous affranchir de cette problématique, nous avons étudié chez la souris, les effets respectifs et combinés d'un régime riche en graisse et/ou de 15 jours d'exposition à des conditions d'hypoxie intermittente (HI) mimant le SAHOS, sur les paramètres vasculaires et métaboliques. L’HI seule n'avait aucun impact sur le bilan-glucido lipidique, la fonction mitochondriale hépatique et la fonction vasculaire des animaux. Les animaux soumis au RRG présentaient une dyslipidémie,une stéatose hépatique, une dysfonction mitochondriale ainsi qu'une une dysfonction endothéliale. Lorsque l’HI était appliquée aux animaux recevant le RRG, l’ensemble de ces dysfonctions vasculaires, hépatiques et mitochondriales était prévenu mais une hyperinslinémie marquée était notée. Ce travail illustre les effets polymorphes de l’HI qui, pour des durées d’exposition courtes, pourrait présenter des effets bénéfiques sur les altérations associées à l’obésité qui contrastent avec les effets délétères à plus long terme décrits dans le SAHOS. / Decades increases the prevalence of many overweigh tassociated diseases including obstructive sleep apnea (OSA). Both OSA and obesity are considered as independent cardio-vascular and metabolic risk factors.The frequent association of OSA and obesity in clinical setting makes difficult to investigate their independent contribution to metabolic and vascular diseases. In the present thesis, we aimed to evaluate the impact of a short term intermittent hypoxia (IH), (animal model of OSA), of a high fat diet (HFD), and of both experimental conditions together (IH and HFD) on the vascular and metabolic outcomes. Short term IH alone had no impact on glucose and lipids levels and mitochondrial and vascular function. Animals fed with HFD presented dyslipidemia, hepatic steatosis, mitochondrial and endothelial dysfunction. Interestingly, when short term IH was applied to HFD fed mice, insulin level was increased, restored endothelial function and mitochondrial activity was restored and limited liver lipid accumulation was limited.Those data underline the polymorphic effects of IH that might target beneficial outcomes when applied for a short term in obesity, which contrast with the deleterious long term outcomes observed in OSA.
177

Meal-time Matters: An 8-week Randomized Control Trial to Examine the Effects of a Daily 18-hour Fast on Diet Quality in College Students

January 2020 (has links)
abstract: ABSTRACT Background. College students’ modifiable health behaviors, including unhealthful eating patterns, predispose them to risk for future cardiometabolic conditions. Purpose. This novel 8-week randomized control parallel-arm study compared the effects of a daily 18-hour Time-Restricted Feeding protocol vs. an 8-hour fast on diet quality in college students. Secondary outcomes were resting morning blood pressure, biomarkers of glucose regulation, biomarkers of lipid metabolism, and anthropometric measures. Methods. Eighteen healthy college students (age = 23 ± 4 years; BMI = 23.2 ± 2.3 kg/m2; MET = 58.8 ± 32.9 min/wk) completed this study. Participants were randomized to a daily 18-hour fasting protocol (Intervention; n = 8) or a daily 8-hour fasting protocol (Control; n = 10) for eight weeks. One ‘cheat’ day was permitted each week. Outcomes were measured at weeks 0 (baseline), 4, and 8. A non-parametric Mann Whitney U test was used to compare the week 4 change from baseline between groups. Statistical significance was set at p≤0.05. Results. Diet quality (p = 0.030) and body weight (p = 0.016) improved from baseline to week 4 for the INV group in comparison to the CON group. The data suggest these improvements may be related to reductions in snacking frequency and increased breakfast consumption. Fasting blood glucose and hip circumference tended to improve for the INV group in comparison to the CON group (p = 0.091 and p = 0.100). However, saturated fat intake tended to increase in the INV group in comparison to the CON group (p = 0.064). Finally, there were no treatment differences between groups (p>0.05) for the 4-week change in total calories, dietary vitamin C, added sugars, resting systolic blood pressure, resting diastolic blood pressure, insulin, homeostatic model assessment for insulin resistance (HOMA-IR), low-density lipoprotein (LDL) cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, waist circumference, or MET. Conclusion. These data, although preliminary, suggest that the 18-hour fasting protocol was effective for improving diet quality and reducing weight in comparison to the 8-hour fasting protocol in healthy college students. Future intervention trials will need to confirm these findings and determine the long-term relevance of these improvements for health outcomes. / Dissertation/Thesis / Doctoral Dissertation Nutrition 2020
178

Functional limit theorem for occupation time processes of intermittent maps / 間欠写像の滞在時間過程に対する関数型極限定理

Sera, Toru 24 November 2020 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22823号 / 理博第4633号 / 新制||理||1666(附属図書館) / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)准教授 矢野 孝次, 教授 泉 正己, 教授 日野 正訓 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM
179

Strategies for the Reduction of Adipose Tissue and Retention of Muscle Mass in Overweight Individuals

Kotarsky, Christopher Joseph January 2020 (has links)
Purpose: The purpose of this study was to determine whether time-restricted feeding (TRF) was an effective dietary strategy for reducing fat mass and preserving fat-free mass while evaluating potential changes in cardiometabolic biomarkers, hormones, muscle performance, and energy and macronutrient intake after eight weeks of aerobic exercise and resistance training in overweight and obese adults. Methods: This study was a randomized, controlled trial. Sedentary, overweight and obese adults (mean ± SD; age: 44.48 ± 7.28 years; BMI: 29.61 ± 2.62 kg/m2; females: 85.71%; males: 14.29%) were randomly assigned to a TRF or normal feeding (NF) dietary strategy group. The TRF group consumed all calories between 1200 and 2000 hours, whereas the NF group ate their typical diet. All groups completed eight weeks of aerobic exercise and supervised resistance training. Body composition, muscle performance, energy and macronutrient intake, physical activity, and physiological variables were assessed week zero and week nine. Results: A total of 21 participants completed the study (NF: n = 10; TRF: n = 11). A mild energy restriction was seen for the TRF (~300 kcal/day, 14.0%) and NF (~250 kcal/d, 11.0%) groups between baseline and week seven. Losses of total body mass were significantly greater for TRF (3.3%) relative to NF (0.2%), of which TRF had significantly greater losses of fat mass (9.0%) compared to NF (3.3%) despite similar reductions in energy intake. Lean mass increased across the intervention for both TRF (0.6%) and NF (1.9%), with no group differences. Conclusion: These data support the use of TRF and concurrent exercise training as a short-term dietary strategy for reducing fat mass and preserving lean mass in overweight and obese adults.
180

Diagnostics of Intermittent Errors / Diagnostik av intermittenta fel

Lindborg, Niklas January 2021 (has links)
Intermittent faults/errors are infamous for being among the most challenging errors to diagnose. It is estimated that more than 80% of the total number of errors in real systems are intermittent errors. Previous research on intermittent errors suggests that they are the prelude to permanent faults. There seems to be a vast knowledge gap in general regarding intermittent errors, both in academia and industry. The term "No Fault Found" might have ingrained a culture of acceptance regarding faults that intermittent errors might cause. This master thesis aims to develop a generic algorithm for diagnostics of intermittent errors that allows for the early isolation of failing sensors, especially at the end of their life spans. It is desirable that Scania can identify intermittent errors efficiently to save maintenance costs and keep customer satisfaction high. Multiple intermittent error detection and diagnostics methods have been produced and tested through simulations in MATLAB. The results suggest that the most important factors when introducing algorithms for intermittent error detection are the sensors' self-diagnostic capabilities and their communication protocol. The developed algorithms can be used for efficient fault isolation, obtaining valuable data for research, and triggering Diagnostic Trouble Codes (DTCs) when the impact of the errors is too significant, which allows for proactive replacement. If the algorithms are introduced as suggested in this master thesis, the knowledge gap can be filled. Consequently, Scania can use the increased knowledge to further improve the algorithms for better detection of intermittent errors and increase the overall performance of Scania vehicles. / Intermittenta fel definieras som fel som ”kommer och går” i ett maskinsystem under dess livslängd och de har ett rykte att vara bland de svåraste felen att diagnostisera. Fel av intermittent karaktär existerar ofta oupptäckta trots att det har uppskattats att mer än 80% av det totala antalet fel i komponenter är intermittenta fel. Tidigare forskning om intermittenta fel tyder på att intermittenta fel, över tid, i princip alltid leder till permanenta fel.  Det verkar dessutom finnas en stor kunskapslucka angående effekten och systempåverkan av intermittenta fel, både inom den akademiska världen och i näringslivet. Vidare kan termen "Inget fel hittats" ha skapat en acceptans-kultur gällande fel i komponenter som intermittenta fel kan ha orsakat.  Detta examensarbete syftar till att utveckla en allmän algoritm för diagnostik av intermittenta fel. Algoritmen ska möjliggöra tidig identifiering av sensorer som håller på att gå sönder eller om de intermittenta felen orsakar för stor systempåverkan, vilket är speciellt viktigt i slutet av sensorernas livslängder. Det är önskvärt att Scania effektivt kan identifiera komponenter med intermittenta fel för att spara underhållskostnader och för att hålla kundnöjdheten hög. Flera intermittenta feldetektering- och diagnostikmetoder har utvecklats och testats med hjälp av simuleringar i MATLAB och Simulink.  Tre sensorer studerades i detta examensarbete. Sensorerna var avgasmottryck sensorn, hög temperatur sensorn och NOx-sensorn. Avgasmottryck sensorn var en analog sensor medan hög temperatur- och NOx sensorn var digitala sensorer. Dessutom hade alla sensorer olika kommunikationsprotokoll och självdiagnostik möjligheter.  För att effektivt kunna utveckla algoritmen kartlades all relevant diagnostik hos de tre sensorerna för att kunna avgöra vilken typ av fel som inte upptäcks av dagens diagnostik. Detta gjordes bland annat genom att studera interna Scania dokumentation och genom att intervjua dem ingenjörer som var ansvariga för den specifika sensorn. De utvecklade algoritmerna fokuserade på att diagnosera dem typer av fel som inte riktigt fångades upp av dagens diagnostik.  Under examensarbetets gång identifierades tre kunder av algoritmen, alla med olika krav och önskemål på vad algoritmen ska leverera. Den första kunden är verkstadsarbetaren. De vill att algoritmen ska ge tydliga instruktioner gällande hur det upptäckta felet ska repareras. Den andra kunden av algoritmen är utvecklingsingenjörerna hos Scania. De vill ha statistik och information från algoritmen som kan användas för att få mer kunskap om intermittenta fel. Den kunskapen skulle kunna användas för att utveckla algoritmerna samt för att göra design ändringar i motorn eller sensorerna för att minska förekomsten av intermittenta fel. Den sista kunden av algoritmen är de lagstiftande myndigheterna. De vill att algoritmerna ska varna föraren av lastbilen om intermittenta fel hittas som kan påverka utsläppen samt om säkerheten har blivit försämrad. Alla dessa kunder togs hänsyn till när algoritmerna utvecklades.  Resultaten tyder på att de viktigaste faktorerna att ta i beaktande vid utveckling av algoritmer för intermittent fel diagnostik är sensorns självdiagnostik och kommunikationsprotokoll. Vidare tyder resultatet från litteraturstudien att de signal symptom som intermittenta fel kan orsaka är toppar och dalar, oscillation, offset, dämpning, överkänslig signal status nedgradering, ingen signal eller maximum/minimum signal. Orsakerna till dessa symptom varierar mellan lösa/glappande kontakter i lödfogen eller kablaget, komponent åldring, oxidation, fukt, läckage eller föroreningar. Ingen ensam algoritm kan detektera alla dessa möjliga symptom i sensorns signaler, därför utvecklades fem olika detektionsmetoder, varje detektionsmetod kan upptäcka olika typer av fel. Tyvärr utvecklades inga detektionsmetoder som kunde hitta intermittenta offset eller dämpningar.  Om algoritmerna implementeras på det sättet som föreslagits i detta examensarbete kan kunskapsluckan fyllas och alla kunder av algoritmen kommer att bli nöjda. Detta görs genom effektiv felisolering, insamling av värdefull information och generering av felkoder om de intermittenta felens påverkan är för stor eller om sensor håller på att gå sönder. Detta skulle möjliggöra proaktiv reperation eller utbyte av sensorer som är på väg att gå sönder. Insamlingen av information rörande intermittenta fel kan Scania använda för att öka kunskapen för att ytterligare förbättra algoritmerna för bättre detektion av intermittenta fel, vilket skulle resultera i ökad prestanda för alla Scania fordon.

Page generated in 0.1016 seconds