INVESTIGATION OF TRIBOLOGICAL CHARACTERISTICS OF AL/NANO SiO2NANOCOMPOSITES PRODUCED BY ACCUMULATIVE ROLL BONDING (ARB) PROCESS

Accumulative roll-bonding process (ARB) is an important severe plastic deformation technique for production of the ultrafine grained, nanostructured and nanocomposite materials in the form of plates and sheets. In the present work, this process used for manufacturing Al/SiO 2 nanocomposites by using Aluminum 1050 alloy sheets and nano sized SiO 2 particles, at ambient temperature. After 8 cycles of ARB process, the tribological properties and wear resistance of produced nanocomposites were investigated. The wear tests by abrasion were performed in a pinon-disc tribometer. Results show that by increasing ARB cycles and the amount of nano powders, the friction coefficient of produced nanocomposites decreases

Prenatal exposure to ambient air pollution and adverse pregnancy outcomes in Ahvaz, Iran: a generalized additive model

Objective: There is some evidence about the short-term effects of air pollutants on adverse pregnancy outcomes. The aim of this study was to determine the association between air pollutants and spontaneous abortion, stillbirth, gestational hypertension, preeclampsia, gestational diabetes and macrosomia in Ahvaz, which is one of the most polluted cities in the Middle East. Methods: Data on adverse pregnancy outcomes and air pollutants including ozone (O3), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), particles with a diameter of less than 10 µm (PM10) and particles with a diameter less than 2.5 µm (PM2.5) were inquired from the Health Department of Ahvaz Jundishapur University of Medical Sciences and the Environmental Protection Agency of Khuzestan Province for the years 2008�2018. A time series analysis using the generalized additive model (GAM) with up to 6-day lags was used. Results: The results showed that the SO2 pollutant on 0, 1, 3, 4, and 6-day lags and PM10 on lag 0 had direct and significant associations with spontaneous abortion. NO, NO2 and CO on 0�6-day lags, and O3 on 6-day lags showed direct and significant associations with preeclampsia. NO and NO2 pollutants showed significant and direct associations with gestational diabetes, during 0- and 6-day lags. NO on 0-, 3- and 4-day lags, CO in all 0�6-day lags and PM2.5 on 1-, 3-, 5-, and 6-day lags showed direct and significant associations with macrosomia. None of the pollutants showed significant associations with stillbirth or gestational hypertension. Conclusions: The results of this study suggest that some air pollutants are associated with spontaneous abortion, preeclampsia, gestational diabetes and macrosomia. This study further emphasizes the need to control ambient air pollution. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature

Vývoj solární střešní tašky s vnitřním chlazením

Tento článek se zabývá vývojem střešní tašky s integrovaným solárním panelem. Tento panel je ochlazován s ohledem na maximalizaci účinnosti. Rozměry tašky jsou podle obecně používané střešní tašky. Plastová solární taška může nahradit běžnou střešní krytinu. Návrh byl ověřen pomocí tepelných simulací a simulací toku v softwaru NX Nastran. Tato řešení FEM byla ověřena měřením na prototypu. Výstupem tohoto výzkumu je prototyp z plastu. Tento materiál byl vybrán z důvodu rychlé a levné výrobyThis paper deals with the development of the roof tile with the integrated solar panel. This panel is cooled down with respect to maximizing of the effectivity. Dimensions of the tile are according generally used roof tile. Plastic solar tile can replace the regular one. The design of the tile was validated by usage of thermal simulations and flow simulations in NX Nastran software. These FEM solutions were validated by the measurement on the prototype. The output of this research is prototype from plastic material. This material was selected because of the fast and cheap production

An enhanced reliability-oriented workforce planning model for process industry using combined fuzzy goal programming and differential evolution approach

Abstract This paper draws on the “human reliability” concept as a structure for gaining insight into the maintenance workforce assessment in a process industry. Human reliability hinges on developing the reliability of humans to a threshold that guides the maintenance workforce to execute accurate decisions within the limits of resources and time allocations. This concept offers a worthwhile point of deviation to encompass three elegant adjustments to literature model in terms of maintenance time, workforce performance and return-on-workforce investments. These fully explain the results of our influence. The presented structure breaks new grounds in maintenance workforce theory and practice from a number of perspectives. First, we have successfully implemented fuzzy goal programming (FGP) and differential evolution (DE) techniques for the solution of optimisation problem in maintenance of a process plant for the first time. The results obtained in this work showed better quality of solution from the DE algorithm compared with those of genetic algorithm and particle swarm optimisation algorithm, thus expressing superiority of the proposed procedure over them. Second, the analytical discourse, which was framed on stochastic theory, focusing on specific application to a process plant in Nigeria is a novelty. The work provides more insights into maintenance workforce planning during overhaul rework and overtime maintenance activities in manufacturing systems and demonstrated capacity in generating substantially helpful information for practice

A Review on Recent Development of Cooling Technologies for Photovoltaic Modules

When converting solar energy to electricity, a big proportion of energy is not converted for electricity but for heating PV cells, resulting in increased cell temperature and reduced electrical efficiency. Many cooling technologies have been developed and used for PV modules to lower cell temperature and boost electric energy yield. However, little crucial review work was proposed to comment cooling technologies for PV modules. Therefore, this paper has provided a thorough review of the up-to-date development of existing cooling technologies for PV modules, and given appropriate comments, comparisons and discussions. According to the ways or principles of cooling, existing cooling technologies have been classified as fluid medium cooling (air cooling, water cooling and nanofluids cooling), optimizing structural configuration cooling and phase change materials cooling. Potential influential factors and sub-methods were collected from the review work, and their contributions and impact have been discussed to guide future studies. Although most cooling technologies reviewed in this paper are matured, there are still problems need to be solved, such as the choice of cooling fluid and its usability for specific regions, the fouling accumulation and cleaning of enhanced heat exchangers with complex structures, the balance between cooling cost and net efficiency of PV modules, the cooling of circulating water in tropical areas and the freezing of circulating water in cold areas. To be advocated, due to efficient heat transfer and spectral filter characters, nanofluids can promote the effective matching of solar energy at both spectral and spatial scales to achieve orderly energy utilization