Maintenance grouping for multi-component systems with availability constraints and limited maintenance teams

International audienceThe paper deals with a maintenance grouping approach for multi-component systems whose components are connected in series. The considered systems are required to serve a sequence of missions with limited breaks/stoppage durations while maintenance teams (repairmen) are limited and may vary over time. The optimization of the maintenance grouping decision for such multi-component systems leads to a NP-complete problem. The aim of the paper is to propose and to optimize a dynamic maintenance decision rule on a rolling horizon. The heuristic optimization scheme for the maintenance decision is developed by implementing two optimization algorithms (genetic algorithm and MULTIFIT) to find an optimal maintenance planning under both availability and limited repairmen constraints. Thanks to the proposed maintenance approach, impacts of availability constraints or/and limited maintenance teams on the maintenance planning and grouping are highlighted. In addition, the proposed grouping approach allows also updating online the maintenance planning in dynamic contexts such as the change of required availability level and/or the change of repairmen over time. A numerical example of a 20-component system is introduced to illustrate the use and the advantages of the proposed approach in the maintenance optimization framework

Planning the restoration of membranes in RO desalination using a digital twin

This paper describes the development of a decision support system (DSS) for evaluating membrane restoration strategy. The engine of the DSS is a digital twin (DT), a virtual representation of wear (degradation) and restoration of membrane elements in a reverse osmosis (RO) pressure vessel. The basis of the DT is a mathematical model that describes an RO vessel as a novel multi-component system in which the wear-states of individual elements (components) are quantified and elements can be swapped or replaced. This contrasts with the contemporary presentation in the literature of a membrane system as a single system. We estimate the parameters of the model using statistical methods. We describe our approach in the context of a case study on the Carlsbad Desalination Plant in California, which suffers from biofouling due to seasonal algae blooms. Our results show a good fit between the observed and the modelled wear-states. Competing policies are compared based on risk, cost, downtime, and number of stoppages. Projections indicate that a significant cost-saving can be achieved while not compromising the integrity of plant

A long range, energy efficient internet of things based drought monitoring system

The climate change and global warning have been appeared as an emerging issue in recent decades. In which, the drought problem has been influenced on economics and life condition in Vietnam. In order to solve this problem, in this paper, we have designed and deployed a long range and energy efficient drought monitoring based on IoT (Internet of Things) for real time applications. After being tested in the real condition, the proposed system has proved its high dependability and effectiveness. The system is promising to become a potential candidate to solve the drought problem in Vietnam

AGING OF WATERBORNE PAINT BASED ON THE ACRYLIC RESIN EMULSION AND ORGANIC PIGMENT

Aging of waterborne paint on the base of acrylic resin emulsion with and without green Luconyl have been investigated by general appearance assessment, adhesion change, FT-IR and discoloration. The obtained results showed that the both of paint-formulas coatings had no cracks, blisters, flacks and there was no change of adhesion during the aging process. However, IR analysis indicated that there were some changes in chemical structures of coating with and without Green Luconyl during aging process. To specify, IR spectrums of initial and aged coating no containing Green Luconyl illustrated aging process led content of O-H and C=C increased significantly but baseline of spectra was fairly unchanged. For coating filled Green Luconyl, IR spectrums’ shape was fairly stable but baseline saw a clear reduce during accelerated weather exposure. Moreover, SEM images indicated that surfaces morphology of samples changed differently depending on in presence of organic pigment. Surface of aged coating without Luconyl saw rougher than surface of coating with Luconyl after aging process. Hence, the weather aging test had more significant influence on paint coating in absence of Luconyl than paint coating in presence of Luconyl. It was explained that the macroradical produced in aging process would attack into conjugated double bonds of Luconyl instead of double bonds of AC-261 leading to aged coating filled Luconyl become more opaque than initial while coating no filled Luconyl had significant changes in chemical structure during aging process. Although this was a hypothesis, it saw a suitable with the obtained results. The paint coating in presence of Luconyl illustrated significant color change, especially, showed the loss of green color while the other paint coating showed slight color change

Jointly power allocation and phase shift optimization for RIS empowered downlink cellular networks

Reconfigurable Intelligent Surfaces (RIS) have been highlighted by the research community as a key enabling technology for the enhancement of next-generation wireless network performance, including energy efficiency, spectral efficiency, and network throughput. This paper investigates how RIS-assisted communication can effectively maximize the downlink throughput of a cellular network. Specifically, the paper considers a communication scenario where a single base station serves multiple ground users with the aid of an RIS placed on a building facade. For such a communication scenario, we considered an optimization problem aimed at maximizing the overall downlink throughput by jointly optimizing power allocation at the base station and phase shift of RIS reflecting elements, subject to power consumption and quality-of-service constraints. To address its non-convex nature, the original optimization problem has been divided into two subproblems. The first one, for power control with fixed phase shift values, is a convex problem that can be easily solved. Subsequently, a phase shift searching procedure to solve the non-convex problem of RIS phase shift optimization has been adopted. The results from numerical simulations show that the proposed method outperforms other conventional methods proposed in the literature. In addition, computational complexity analysis has been conducted to prove the low complexity of the proposed method

Depression and its associated factors among pregnant women in central Vietnam.

To date, little attention has been given to prenatal depression, especially in low and middle-income countries. The aim of this research was to assess the prevalence of depression and its associated factors amongst pregnant women in a central Vietnamese city. This cross-sectional study included 150 pregnant women from 29 to 40 weeks of gestation, from eight wards of Hue city, via quota sampling from February to May 2019. We employed the Patient Health Questionnaire (PHQ-9) to assess depression. Findings suggest the need to provide routine screening of pregnant women in primary care for depressive symptoms and other mental health problems.This is part of the EBLS proejct of which Prof Eisner is PI. Botnar Fondation is the sponso

Intergenerational effects of violence on women's perinatal wellbeing and infant health outcomes: evidence from a birth cohort study in Central Vietnam.

BACKGROUND: Girls exposed to violence have a high risk of being victimized as adults and are more likely than non-abused women to have children who are treated violently. This intergenerational transmission may be especially serious when women suffer violence during pregnancy and early motherhood, as it impairs maternal wellbeing and infant health and development. This study examined the intergenerational effects of being exposed to childhood maltreatment (CM) and prenatal intimate partner violence (p-IPV) on perinatal mental distress and birth outcomes in central Vietnam. METHODS: A birth cohort study in Hue City, Vietnam was conducted with 150 women in the third trimester of pregnancy (Wave 1) and 3 months after childbirth (Wave 2). Using multivariable logistic regression models, augmented inverse-probability-weighted estimators and structural equation modelling (SEM), we analyzed a theoretical model by evaluating adjusted risk differences and pathways between CM, p-IPV and subsequent perinatal adversity and indicators of infant health problems. RESULTS: One in two pregnant women experienced at least one form of CM (55.03%) and one in ten pregnant women experienced both CM and p-IPV (10.67%). Mothers who experienced p-IPV or witnessed IPV as a child were approximately twice as likely to experience poor mental health during pregnancy [ARR 1.94, 95% CI (1.20-3.15)]. Infants had a two-fold higher risk of adverse birth outcomes (low birth weight, preterm birth, admission to neonatal intensive care) [ARR 2.45 95% CI (1.42, 4.25)] if their mothers experienced any form of p-IPV, with greater risk if their mothers were exposed to both CM and p-IPV [ARR 3.45 95% CI (1.40, 8.53)]. Notably, significant pathways to p-IPV were found via adverse childhood experience (ACE) events (β = 0.13), neighborhood disorder (β = 0.14) and partner support (β = - 1.3). CONCLUSION: These results emphasize the detrimental and prolonged nature of the effect of violence during childhood and pregnancy. Exposure to childhood maltreatment and violence during pregnancy increases the risk of maternal mental health difficulties and adverse birth outcomes. Antenatal care systems need to be responsive to women's previous experiences of violence and maternal mental health. The significant protective role of partner support and social support should also be considered when designing tailored interventions to address violence during pregnancy

Influence of Sintering Temperature on Low-field Spin-polarized Tunneling Magnetoresistance of La0.7Ca0.3MnO3

In this study we report the effect of sintering temperature on the low field magnetoresistance (LFMR) of La0.7Ca0.3MnO3 manganite synthesized through sol-gel technique. The La0.7Ca0.3MnO3 has been sintered at 600°C, 700°C, 800°C, 900°C and 1200°C. The crystallite as well as particle size also show strong dependence on the sintering temperature. While the ferromagnetic – paramagnetic (FM-PM) transition temperature remains almost constant, the metal – insulation transition temperature drop gradual and the low field magnetoresistance (LFMR) increase with a decrease in grain size. We have analyzed our data based on the spin – polarized transport of conduction electrons at the grain boundaries

The Exploration of Effects of Chinese Cultural Values on the Attitudes and Behaviors of Chinese Restaurateurs Toward Food Safety Training

Citation: Liu, P., & Kwon, J. (2013). The exploration of effects of Chinese cultural values on the attitudes and behaviors of Chinese restaurateurs toward food safety training. Journal of Environmental Health, 75(10), 38-46.Foodborne illness is a challenge in the production and service of ethnic foods. The purpose of the study described in this article was to explore variables influencing the behaviors of U.S. Chinese restaurant owners/operators regarding the provision of food safety training in their restaurants. Seventeen major Chinese cultural values were identified through individual interviews with 20 Chinese restaurant owners/operators. Most participants felt satisfied with their previous health inspections. Several expressed having difficulty, however, following the health inspectors’ instructions and in understanding the health inspection report. A few participants provided food safety training to their employees due to state law. Lack of money, time, labor/energy, and a perceived need for food safety training were recognized as major challenges to providing food safety training in Chinese restaurants. Videos, case studies, and food safety training handbooks were the most preferred food safety training methods of Chinese restaurant owners/operators, and Chinese was the preferred language in which to conduct the training