Inactivation of Fecal coliforms during solar and photocatalytic disinfection by zinc oxide (ZnO) nanoparticles in compound parabolic concentrators (CPCs)

Water samples of 0, 50, and 100 nephelometric turbidity units (NTU) spiked with fecal coliforms (107 CFU/ml) were exposed to natural sunshine in 1l quartz glass tubes fitted with rectors' compound parabolic concentrators CPCS at two forms CPC1 (whit nanoparticle zinc oxide) and CPC2(without nanoparticle zinc oxide). The samples were characterized using the X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). On clear days, the complete inactivation times (more than 7-log unit reduction in bacterial population) in the systems with CPC1, and CPC2 were 15, and 30 min, respectively. The maximum temperatures obtained in the water samples were 80°C for CPC1, and 82°C for CPC2. The use of CPC1 with hydroxyl radicals (OH·) production significantly improved the efficiency of the old CPCS technique, since these systems (CPC1-2) shortened the exposure times to solar radiation and also minimized the negative effects of turbidity and also regrowth was zero in the disinfected samples. Due to two simultaneous effects of high temperatures and UV, regrowth in most ways of solar disinfection was not seen in these examples. Overall, this technology has been proved to be a good enhancement method to inactivate microorganisms under real conditions and represents a good alternative technique to drinking water treatment. © 2019, Islamic Azad University

Performance index improvement of a double-pipe cooler with MgO/water-ethylene glycol (50:50) nano-suspension

A series of tests was conducted to unlock the potential application of MgO/water-EG (ethylene glycol) nanofluids (NF) in a double-pipe heat exchanger (HEX). The overall heat transfer coefficient (HTC), the inlet temperature of the working fluid, the fluid pressure drop (FPD), friction factor (FF) and the hydraulic performance index of the NF within the HEX were experimentally measured. Fouling of nanoparticles (NPs) within the Hex was also studied and modelled using asymptotic particulate fouling model. Results showed that MgO NPs can enhance the HTC by 39% at Re=10,500 and wt.% = 0.3 in the turbulent regime. Also, the presence of MgO NPs augmented the FF and the FPD values. The former was enhanced 33.8%, while the latter was augmented by 37% both at wt.% = 0.3 and at Reynolds number = 10,500. Results also revealed that the formation of porous particulate fouling layer on the internal wall of the inner tube creates a fouling thermal resistance which changes asymptotically with time. Overall, MgO/water-ethylene glycol shows a great potential to be used as a coolant within a HEX.H. Arya, M.M. Sarafraz, O. Pourmehran, M. Arjomand

Negated bio-events: Analysis and identification

Background: Negation occurs frequently in scientific literature, especially in biomedical literature. It has previously been reported that around 13% of sentences found in biomedical research articles contain negation. Historically, the main motivation for identifying negated events has been to ensure their exclusion from lists of extracted interactions. However, recently, there has been a growing interest in negative results, which has resulted in negation detection being identified as a key challenge in biomedical relation extraction. In this article, we focus on the problem of identifying negated bio-events, given gold standard event annotations.Results: We have conducted a detailed analysis of three open access bio-event corpora containing negation information (i.e., GENIA Event, BioInfer and BioNLP'09 ST), and have identified the main types of negated bio-events. We have analysed the key aspects of a machine learning solution to the problem of detecting negated events, including selection of negation cues, feature engineering and the choice of learning algorithm. Combining the best solutions for each aspect of the problem, we propose a novel framework for the identification of negated bio-events. We have evaluated our system on each of the three open access corpora mentioned above. The performance of the system significantly surpasses the best results previously reported on the BioNLP'09 ST corpus, and achieves even better results on the GENIA Event and BioInfer corpora, both of which contain more varied and complex events.Conclusions: Recently, in the field of biomedical text mining, the development and enhancement of event-based systems has received significant interest. The ability to identify negated events is a key performance element for these systems. We have conducted the first detailed study on the analysis and identification of negated bio-events. Our proposed framework can be integrated with state-of-the-art event extraction systems. The resulting systems will be able to extract bio-events with attached polarities from textual documents, which can serve as the foundation for more elaborate systems that are able to detect mutually contradicting bio-events. © 2013 Nawaz et al.; licensee BioMed Central Ltd

Pool boiling under the magnetic environment: experimental study on the role of magnetism in particulate fouling and bubbling of iron oxide/ethylene glycol nano-suspension

A set of experiments were conducted in a high-fidelity test rig to develop a new understanding on the role of magnetic field on the particulate fouling of iron oxide/ethylene glycol nano-suspension under a high heat flux pool boiling regime. Nano-suspensions were prepared at mass concentrations 0.1 and 0.2% and the tests were conducted up to heat flux 900 kW/m². Influence of different operating parameters including heat flux, mass concentration of nanoparticles, the strength of magnetic field and bulk temperature on the pool boiling heat transfer coefficient (as an index for thermal performance) and particulate fouling resistance of the surface was experimentally investigated and discussed. Results showed that the presence of magnetic field lowers the fouling resistance and increases the heat transfer coefficient at any mass concentrations of test nanofluid. Likewise, an increase in the bulk temperature of nanofluid increased the heat transfer coefficient as well. For any mass concentrations, presence of the magnetic field suppressed the fouling rate. For all the experiments, the fouling thermal resistance reached the asymptotic point in which the fouling resistance remains constant. The value of the asymptotic point was increased with an increase in the mass concentration of nanofluid. Eventually, magnetic field was found to mitigate the fouling formation of nanoparticles at any heat fluxes, mass concentration and bulk temperature of nanofluids.H. Arya, M.M. Sarafraz, M. Arjomand

Heat transfer and fluid flow of MgO/ethylene glycol in a corrugated heat exchanger

The present work aims to investigate the thermo-hydraulic performance of a counter-current corrugated plate heat exchanger working with MgO/ethylene glycol nanofluid. MgO nanoparticles were dispersed in ethylene glycol at different weight (mass) concentrations of 0.1 %, 0.2 % and 0.3 % and nanofluids were introduced to a heat exchanger in form of a counter-current flow to exchange heat with water. The test rig provided conditions to measure the influence of different operating parameters such as fluid flow, mass concentration and inlet temperature of the nanofluid on heat transfer coefficient, pressure drop, and thermal performance index of the heat exchanger. Results showed that flow rate and mass concentration can intensify the convective heat transfer coefficient. However, they both increase the pressure drop of the system. The heat transfer coefficient, pressure drop was found to be enhanced by 35 % and 85 %, respectively at wt.% = 0.3. Interestingly, inlet temperature was found to only increase the heat transfer coefficient slightly (up to 9.8 % at wt.% = 0.3) and had no influence on the values of pressure drop. The presence of MgO nanoparticles was found to increase the thermo-hydraulic performance index of the heat exchanger by 34 %.H. Arya, M. M. Sarafraz and M. Arjomand

Flow boiling heat transfer to MgO-therminol 66 heat transfer fluid: Experimental assessment and correlation development

An experimental investigation was performed on the flow boiling heat transfer characteristics of MgO/therminol 66 nanofluid as a potential coolant on a copper-made disc. Nanofluids were prepared using two step method at wt.%=0.1, and wt.%=0.3. Results showed that the presence of MgO/therminol 66 increases the flow boiling heat transfer coefficient in comparison with the base fluid. However, with an increase in the mass concentration of nanoparticles, the heat transfer coefficient decreased. Results also revealed that bubble formation induces a pressure drop within the test section. Heat flux had no influence on the pressure drop, while an increase in the fluid flow rate caused an increase in the pressure drop. It was also found that the heat transfer coefficient decreased with operating time due to the presence of nanoparticles on the boiling surface resulting in the creation of thermal resistance on the surface. Also, an asymptotic behavior for the fouling thermal resistance over the time was registered. Two correlations were re-developed to accurately predict the heat transfer coefficient and fouling thermal resistance of the system. Experiments proved that MgO nanoparticles offer a potential to be used in thermal engineering systems with boiling heat transfer mechanism. The maximum enhancement for the heat transfer coefficient was 23.7% at wt.%=0.1. For wt.%=0.2 and wt.%=0.3, the maximum enhancement of 16.2% and 13.3%, were achieved, respectively.M.M. Sarafraz, H. Arya, M. Saeedi, D. Ahmad

Heat transfer and pressure drop characteristics of MgO nanofluid in a double pipe heat exchanger

The present work aims to investigate the plausible application of MgO-ethylene glycol as a heat transfer fluid in a double-pipe heat exchanger. The nanofluid was prepared using a two-step method at weight concentrations of 0.1, 0.2 and 0.3%. The test rig provided conditions to measure the convective heat transfer coefficient, pressure drop and friction factor of the system. Influence of the different operating parameters such as flow rate, mass concentration of nanoparticles and inlet temperature of nanofluid to the heat exchanger on the heat transfer coefficient and pressure drop was experimentally investigated. Results showed that the heat transfer coefficient within the heat exchanger can be enhanced by 27% for wt.% = 0.3 in comparison with the base fluid (ethylene glycol). It was also found that the presence of MgO nanoparticles increased the pressure drop by 35% at wt.% = 0.3. The friction factor of the system decreased nonlinearly with an increase in the Reynold number and it followed the trend of 64/Re equation. An increase in the mass concentration of nanoparticles increased the friction factor and the maximum friction factor enhancement was 32% belonging to the nanofluid with mass concentration of wt.% = 0.3. Likewise, inlet temperature was found to have a very slight influence on the heat transfer coefficient and no effect on the friction factor and pressure drop of the system. The thermo-physical properties of MgO-ethylene glycol nanofluid was also experimentally measured at various temperatures.H. Arya, M.M. Sarafraz, O. Pourmehran, M. Arjomand