The application of Microwave Irradiation has become a frequent heating source in organic and inorganic materials synthesis. Inspired by this vast achievement, the use of microwave irradiation is highly studied for polymer synthesis. The influence of modified microwave system on the solubility and kinetics properties of the polyethersulfone (PES) dope solution has been investigated. A modified microwave (MW) assisted closed heating system was applied to prepare the PES dope solution in single solvent; dimethylformamide (DMF) and mixture of two solvents DMF/acetone for membrane fabrication. Providentially, most of the synthetic polymeric membrane materials are polar and dipolar which is a very important factor in microwave processing. New MW systems have given incredible properties in terms of viscosity, shear stress, shear rate and yield stress of polymer dope solutions. The results revealed that MW assisted pure PES solution exhibits pseudoplastic and Newtonian behaviour respectively. However, PES solution containing the two solvent system exhibits dilatants behaviour, which obeys the power-law. The apparent viscosity of the PES dope solutions prepared using the DMF is lower as compared to those prepared using the DMF/acetone. Rheological properties measured include apparent viscosity at various shear rates. Subsequently the flow behaviour (n) and consistency index (k) is determined.
The objective of this study is to investigate the effects of hydrogen peroxide (H2O2) on the combustion enhancer and performance of liquefied petroleum gas (LPG) on spark ignition engines. LPG has a simpler hydrocarbon structure than conventional fuels. H2O2 is recently reported as a renewable fuel and to be a low-emission high-quality fuel replacement. The addition of H2O2 at various wt. percentage concentrations in to LPG at mixture (LPG/H2O2) form will be used for the experiments and measurements can be made to study the performance, combustion, and emissions characteristics. The performance of in starting from lean LPG until obtaining a better composition can reduce the LPG fuel consumption. The theory behind this concept is that the addition of hydrogen peroxide can extend the lean operation limit, improve the lean burn ability, decrease burn duration and controlling the exhaust emission by reducing green house gaseous.
Recently, a swarm-based method called Artificial Hummingbird Algorithm (AHA) has been proposed for solving optimization problems. The AHA algorithm mimics the unique flight capabilities and intelligent foraging techniques of hummingbirds in their environment. In this paper, we propose a modified version of the AHA combined with genetic operators called mAHA. The experimental results show that the proposed mAHA improved the convergence speed and achieved better effective search results. Consequently, the proposed mAHA was used for the first time to find the global maximum power point (MPP). Low efficiency is a drawback of photovoltaic (PV) systems that explicitly use shading. Normally, the PV characteristic curve has an MPP when irradiance is uniform. Therefore, this MPP can be easily achieved with conventional tracking systems. With shadows, however, the conditions are completely different, and the PV characteristic has multiple MPPs (i.e., some local MPPs and a single global MPP). Traditional MPP tracking approaches cannot distinguish between local MPPs and global MPPs, and thus simply get stuck at the local MPP. Consequently, an optimized MPPT with a metaheuristic algorithm is required to determine the global MPP. Most MPPT techniques require more than one sensor, e.g., voltage, current, irradiance, and temperature sensors. This increases the cost of the control system. In the current research, a simple global MPPT method with only one sensor is proposed for PV systems considering the shadow conditions. Two shadow scenarios are considered to evaluate the superiority of the proposed mAHA. The obtained results show the superiority of the proposed single sensor based MPPT method for PV systems.
Due to the scarcity, randomness, and extremity of rainfall events in arid regions, planning and management of water resources are essential.Rainfall in many arid regions such as Saudi Arabia is characterized by high intensity and short duration during which flash floods occur and cause not only major loss in life and structures but also a huge loss of clean water.Understanding the relationship between rainfall and runoff is the key issue in the management and control of water resources.In this study, two approaches have been applied using Hydrologic Engineering Center's Hydraulic Modeling System model to simulate flood hydrographs of a mountainous watershed located on the west side of Saudi Arabia.The first approach was based on incorporating losses through the soil conservation service (SCS) curve number and SCS unit hydrograph.The second approach was based on effective rainfall in which excess rainfall was computed by Horton's infiltration method and the Phi index method.Results revealed that the performance of losses incorporation approach was poor in simulating runoff hydrographs in all studied storms.Its main drawback was the ineffective representation of flow mass conservation and the early generation of runoff due to rainfall input.In contrast, the effective rainfall approach simulated runoff hydrographs efficiently; moreover, results were comparable with many of those reported in the literature.The two critical hydrograph parameters of peak flow and time to peak were simulated accurately by Phi index method and Horton's infiltration method.The sensitivity analysis showed that the peak flow is directly proportional to the curve number and inversely proportional to the initial abstraction.From water management point of view, the simulated hydrographs added a valuable piece of information about the quantification of lost and stored rainwater.About 55%-70% of rainwater infiltrates through the soil profile and recharges the underlined groundwater reservoir, hence becomes a major source of water in the region.
The influence of TEOS on the rheological properties of PVDF and poly(vinylidene fluoride-co-hexafluoropropylene) was investigated. The addition of TEOS to low molecular weight PVDF results in pseudoplastic behavior. The exception is PVDF containing 5 wt%. TEOS, which shows dilation behavior. Similar behavior has high molecular weight PVDF with the addition of 2 wt.% TEOS and low molecular weight copolymer with and without TEOS. The influence of temperature on the viscosity and activation energy of the tested PVDF solutions and the influence of TEOS on the average molecular weight were also examined.
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