Suchergebnisse

Today, industrial systems become more and more complex. The complexity is due partly to the structure of the system that cannot be reduced to classic structure reliability (series structures, parallel structures, series-parallel structures, etc), secondly the consideration of components with gradual degradation phenomena that can be monitored. This leads to the main purpose of this thesis on the development of predictive maintenance strategies for complex multi-component systems. The proposed policies provide maintenance grouping strategies to take advantage of the economic dependence between components. The predictive reliability of components and importance measures allowing taking into account the structure of the system and economic dependence are developed to construct the grouping decision rules. Moreover, a joint decision rule for maintenance and spare parts provisioning is also studied.All the conducted studies show the interest in the consideration of the predictive reliability of components, economic dependencies as well as complex structure of the system in maintenance decisions and spare parts provisioning. The advantage of the developed strategies is confirmed by comparing with the other existing strategies in the literature ; Aujourd'hui, les systèmes industriels deviennent de plus en plus complexes. Cette complexité est due d'une part à la structure du système qui ne se résume pas à des structures classiques en fiabilité, d'autre part à la prise en compte de composants présentant des phénomènes de dégradation graduelle que des systèmes de monitoring permettent de surveiller. Ceci mène à l'objectif de cette thèse portant sur le développement des stratégies de maintenance prévisionnelle pour des systèmes multi-composants complexes. Les politiques envisagées proposent notamment des stratégies de regroupement de composants permettant de tirer des dépendances économiques identifiées. Des facteurs d'importance permettant de prendre en compte la structure du système et la dépendance économique sont développés et combinés avec les évaluations de fiabilité prévisionnelle des composants pour l'élaboration de règles de décision de regroupement. De plus, un couplage des règles de décision de maintenance et de gestion des stocks est également étudié. L'ensemble des études menées montrent l'intérêt de la prise en compte de la fiabilité prévisionnelle des composants, des dépendances économiques et de la structure complexe du système dans l'aide à la décision de maintenance et de gestion des stocks. L'avantage des stratégies développées est vérifié en les comparant à d'autres existantes dans la littérature

Today, industrial systems become more and more complex. The complexity is due partly to the structure of the system that cannot be reduced to classic structure reliability (series structures, parallel structures, series-parallel structures, etc), secondly the consideration of components with gradual degradation phenomena that can be monitored. This leads to the main purpose of this thesis on the development of predictive maintenance strategies for complex multi-component systems. The proposed policies provide maintenance grouping strategies to take advantage of the economic dependence between components. The predictive reliability of components and importance measures allowing taking into account the structure of the system and economic dependence are developed to construct the grouping decision rules. Moreover, a joint decision rule for maintenance and spare parts provisioning is also studied.All the conducted studies show the interest in the consideration of the predictive reliability of components, economic dependencies as well as complex structure of the system in maintenance decisions and spare parts provisioning. The advantage of the developed strategies is confirmed by comparing with the other existing strategies in the literature ; Aujourd'hui, les systèmes industriels deviennent de plus en plus complexes. Cette complexité est due d'une part à la structure du système qui ne se résume pas à des structures classiques en fiabilité, d'autre part à la prise en compte de composants présentant des phénomènes de dégradation graduelle que des systèmes de monitoring permettent de surveiller. Ceci mène à l'objectif de cette thèse portant sur le développement des stratégies de maintenance prévisionnelle pour des systèmes multi-composants complexes. Les politiques envisagées proposent notamment des stratégies de regroupement de composants permettant de tirer des dépendances économiques identifiées. Des facteurs d'importance permettant de prendre en compte la structure du système et la dépendance économique sont ...

Vietnam fish producers have little adaptive financial strategies to deal with fish mortality from diseases or climatic events. Government of Vietnam (GOV) decided to implement an agriculture insurance scheme starting with a pilot program during the period 2011–2013. The objectives of the insurance pilot program were to protect rural livelihoods and to improve the efficiency of the insurance market. After the completion of the three-year pilot scheme, GOV intended to encourage the insurance companies to privatize the insurance program nationwide. The question to be asked: Was the pilot insurance well planned and are the results sufficient to encourage the private sector to commercialize the venture? The literature search showed that the aquaculture insurance program was a total disaster. The feasibility study failure was due to a lack of a prototype model for a dry run to examine the operation. There was no legal document but a set of decisions and circulars. The pilot aquaculture insurance program had only one product for the use of clients. There was an absence of a monitoring and evaluation system in place. Underwriters had no data and guide to properly evaluate claims. The heavily subsidized program encouraged price distortion, adverse selection and moral hazard.

AbstractIntroductionIn people living with human immunodeficiency virus (PLHIV), traditional cardiovascular risk factors, exposure to HIV per se and antiretroviral therapy (ART) are assumed to contribute to cardiometabolic diseases. Nevertheless, controversy exists on the relationship of HIV and ART with diabetes. To clarify the relationship between HIV and type 2 diabetes, this review determined, in PLHIV in Africa, diabetes and prediabetes prevalence, and the extent to which their relationship was modified by socio‐demographic characteristics, body mass index (BMI), diagnostic definitions used for diabetes and prediabetes, and HIV‐related characteristics, including CD4 count, and use and duration of ART.MethodsFor this systematic review and meta‐analysis (PROSPERO registration CRD42021231547), a comprehensive search of major databases (PubMed‐MEDLINE, Scopus, Web of Science, Google Scholar and WHO Global Health Library) was conducted. Original research articles published between 2000 and 2021 in English and French were included, irrespective of study design, data collection techniques and diagnostic definitions used. Observational studies comprising at least 30 PLHIV and reporting on diabetes and/or prediabetes prevalence in Africa were included. Study‐specific estimates were pooled using random effects models to generate the overall prevalence for each diagnostic definition. Data analyses used R statistical software and "meta" package.ResultsOf the 2614 records initially screened, 366 full‐text articles were assessed for eligibility and 61 were selected. In the systematic review, all studies were cross‐sectional by design and clinic‐based, except for five population‐based studies. Across studies included in the meta‐analysis, the proportion of men was 16–84%. Mean/median age was 30–62 years. Among 86,412 and 7976 participants, diabetes and prediabetes prevalence rates were 5.1% (95% CI: 4.3–5.9) and 15.1% (9.7–21.5). Self‐reported diabetes (3.5%) was lower than when combined with biochemical assessments (6.2%; 7.2%).DiscussionWhile not statistically significant, diabetes and prediabetes were higher with greater BMI, in older participants, urban residents and more recent publications. Diabetes and prediabetes were not significantly different by HIV‐related factors, including CD4 count and ART.ConclusionsAlthough HIV‐related factors did not modify prevalence, the diabetes burden in African PLHIV was considerable with suboptimal detection, and likely influenced by traditional risk factors. Furthermore, high prediabetes prevalence foreshadows substantial increases in future diabetes in African PLHIV.