A comparative study of the tensile properties of compression molded and 3D printed PLA specimens in dry and water saturated conditions

Journal of Mechanical Science and Technology - This research work presents a comparative study of the tensile properties of polylactic acid (PLA) specimens per ASTM D638-14 fabricated by...     

Mathematical and neural network models for predicting the electrical performance of a PV/T system

There are many photovoltaic/thermal (PV/T) systems' designs that are used mainly to reduce the temperature of the PV cell by using a thermal medium to cool the photovoltaic module. In this study, a PV/T system uses nano‐phase change material (PCM) and nanofluid cooling system was adopted. Three cooling models were compared using nanofluid (SiC‐water) and nano‐PCM to improve the performance and productivity of the PV/T system. Three mathematical models were developed for linear prediction, and their results were compared with the predicted artificial neural network results, results were verified, and experimental results were appropriate. Three common evaluation criteria were adopted to compare that the results of proposed forecasting models with other models developed in many research studies are done, including the R², mean square error (MSE), and root‐mean‐square error (RMSE). Besides, different experiments were implemented using varying number of hidden layers to ensure that the proposed neural network models achieved the best results. The best neural prediction models deployed in this study resulted in good R² score of 0.81 and MSE of 0.0361 and RMSE and RMSE rate is 0.371. Mathematical models have proven their high potential to easily determine the future outcomes with the preferable circumstances for any PV/T system in a precise way to reduce the error rate to the lowest level.     

Biochemical and molecular characterization of novel PAH-degrading bacteria isolated from polluted soil and sludge

Polycyclic aromatic hydrocarbons (PAHs) containing more than three rings are mainly less biodegradable. Therefore, the isolation of PAHs-degrading bacteria is of great importance to be augmented for bioremediation of polluted sites with PAHs. PAHs-degrading bacteria were isolated from contaminated sites of an oil refinery. The strains were confirmed by biochemical tests and 16S rRNA, which were Stenotrophomonas maltophilia (two strains), Thermomonas koreensis (three strains), Achromobacter (two strains), Pseudomonas stutzeri (one strain), Azospirillum brasilense (one strain) and Brevibacillus brevis (one strain). The isolate strains can be applied as a bacterial consortium for purification of polluted soil with high levels of PAHs.     

A high‐voltage gain nonisolated noncoupled inductor based multi‐input DC‐DC topology with reduced number of components for renewable energy systems

This paper proposes a modular nonisolated noncoupled inductor‐based high‐voltage gain multi‐input DC‐DC converter. Despite the high‐voltage gain of the proposed topology, the average of normalized voltage stress (NVS) on its switches/diodes is low. This property leads to less loss and cost of switches/diodes. Using the same number of components, the proposed topology produces higher voltage gains, in comparison with recently presented high step‐up topologies. Also, the proposed topology utilizes less number of components (capacitors, inductors, diodes, and switches) for producing a desired voltage gain, which can reduce the size, mass, cost, complexity, and losses and improve the efficiency of converter. Continuous current of input sources is another main advantage of the proposed topology. All the abovementioned characteristics have made the proposed topology very suitable for renewable energy systems (or even hybrid/electric vehicles). Design considerations of the proposed topology have also been presented. For better evaluation, the proposed topology has been compared with some of recently presented high step‐up structures, from viewpoints of producible voltage gain, number of components, and normalized voltage stress (NVS) on switches/diodes. Finally, the prototype of 2‐input version has been experimentally implemented. Obtained experimental results confirm appropriate performance of the proposed topology.     

A comprehensive experimental evaluation of asphaltene dispersants for injection under reservoir conditions

As the efficiency of dispersants with different origins is questionable for each typical oil sample, the present study provides a reproducible and reliable method for screening asphaltene dispersants for a typical asphaltenic crude oil. Four different asphaltene dispersants (polyisobutylene succinimide, polyisobutylene succinic ester, nonylphenol-formaldehyde resin modified by polyamines, and rapeseed oil amide) were prepared and their performance on two oils from an Iranian field under laboratory and reservoir conditions was studied. A thorough analysis including ash content and SARA tests was performed on the solid asphaltene particles to characterize the nature of deposits. Then a highly efficient carrier fluid, which is crucial when injecting dispersant into the wells, was selected from a variety of chemicals by comparing their solubility. In the next step, using an optical microscope, a viscometer, and a Turbiscan, the screening of dispersants under laboratory conditions was done on a mixture of dead oil and dispersant to evaluate the onset of asphaltene precipitation and its stability when titrating by a precipitant. Finally, two different mixtures of the efficient dispersants, live oil, and carrier fluid were used with the solid detection system (SDS) and the filtration method to examine their effects on the onset pressure of asphaltene precipitation and the asphaltene content of the crude oil under reservoir conditions. The results show that the combination of experimental methods used in this work could be consistently applied to screening asphaltene dispersants. Among the four different dispersants applied here, the dispersant based on nonylphenol-formaldehyde resin modified by polyamines showed the best performance on the available live oils. This chemical modified the onset pressure of asphaltene precipitation of light oil from 4300 psi to about 3600 psi and decreased the precipitated asphaltene of heavy oil by about 30 %.     

Relay coordination and protection failure effects on reliability indices in an interconnected sub-transmission system

Protection system failure is the main cause of cascading outages. It has been shown that the hidden failures lead to cascading outages. However, the effects of the coordination method as well as the hidden failure of the protection systems have not been investigated yet. In this paper, an algorithm based on sequential Monte Carlo simulation is proposed to find the reliability indices for different overcurrent relay coordination methods. The proposed algorithm is applied to the results of different relay coordination methods of a real network. The indices SAIFI, CAIDI, CAIFI and ENS for the results of different relay coordination methods are obtained strictly based on the contribution of the protection failure issues. Then, a comparison is made between the results of the different relay coordination methods in order to show how the coordination methods affect the reliability indices.     

Sorption properties of hydrogen-selective PDMS/zeolite 4A mixed matrix membrane

The present study explores the fundamental science of estimating sorption of gases in membranes comprised of inorganic porous fillers within a polymer matrix with a novel semi-empirical correlation. The sorption properties of H₂, C₃H₈, CO₂ and CH₄ were determined in polydimethylsiloxane (PDMS)/zeolite 4A mixed matrix membranes (MMMs) to assess the viability of these membranes for hydrogen purification and natural gas sweetening. Zeolite filling in MMMs results an increase in solubility over neat PDMS membrane. In addition, incorporation of zeolite 4A to PDMS membrane improved H₂ permeation and H₂/CH₄ selectivity. The results confirmed that zeolite 4A can significantly improve the separation properties of poorly H₂-selective PDMS membrane from 0.7 up to 11 and this overcomes the Robeson upper-bound limitation. This improvement was explained referring the Flory–Huggins interaction parameter within MMMs.