Published: Mar 17, 2022
Modern Power Distribution Networks (MPDNs) are no longer passive because Distributed Generations (DGs) are integrated with them to enhance system reliability and power quality. For this reason, load modeling has to be updated to capture the new dynamics of active DNs. This paper presents a composite load modeling for a grid-connected photovoltaic (PV) distribution network using the Levenberg-Marquardt algorithm in the deep learning feed-forward neural network approach. Load modeling is constructing a relationship between input excitation(s) and output response(s); it can be used for simulation studies, stability analysis, and control/protection design. A grid-connected PV distribution network was modeled in Matlab/Simulink and generates data for training and model estimation. The estimated model was tested and validated using a laboratory experimental test bed. Results of the model exhibit a good fitness of 99.8% and 97.2% in active and reactive power models respectively during training. While 97.84% and 94.65% respectively were obtained during testing. The estimation errors were found to be 0.0025 and 0.0049 for active and reactive powers respectively with 0.0473 and 0.0701 corresponding errors in testing.
Determination of soluble hexavalent chromium in samples of Portland cement from Brazilian cement manufacturers
Urbanization growing is nowadays highlighted in the big cities. Therefore, it is necessary to increase the production of cement, which is used in several areas of civil construction, to supplement the growing demand. Thus, the objective of this study was to determine the content of hexavalent soluble chromium in Portland cement samples from different cement industries in São Paulo state, Brazil, since this chemical species can cause adverse health effects as well as being a potential human carcinogenic for those who manipulate it. In Brazil, the emission of Cr6+ in the cement has no restrictions, since there is no current Brazilian law that determines the maximum concentration of it, whereas, in Europe, the current law 2003/53/EC establishes a maximum of 2 mg.kg-1. So, the Cr6+ content for different cement samples was determined by spectrophotometry based on the European standard EN196-10/2006. It was found by the analysis that among all types of cement produced in São Paulo, the only one that did not exceed the standard limit was the CP III, probably because this kind of cement has a high concentration of additions in its composition, responsible for diluting thereby chromium content. The other types of cement exceeded the established limit. It was concluded that Brazil urgently needs a law to regulate the hexavalent soluble chromium emission present in Portland cement to minimize the environmental and health effects that the cement out of specification may cause.
Optimization of Pelleting Parameters for Producing Composite Pellets Using Zeolitic Material From Fly Ash
Zeolitic material in powder form was prepared from fly ash by direct activation treatment. The resulted fly ash-based zeolite was pelletizing and the effect of different inorganic (calcium hydroxide, bentonite, kaolinite) and organic (dextrin) binders with varying percentage was investigated. The zeolitic materials were analyzed by XRF, XRD, SEM, FTIR, TG-DTG and Nitrogen adsorption/desorption isotherm. Compression and impact tests have been used to study the deformation and breakage behaviour of spherical granules. The best performance was obtained by zeolite granular containing 5 wt.% bentonite and 5 wt.% kaolinite with mechanical strength and satisfactory water resistance. The synthesis of pelletized zeolite from by-products derived from coal combustion provides not only environmental and economic benefits, but also contributes to achieving the principles of sustainable development.
The Effect of Portland Cement on Fly Ash Bottom Ash Geopolymer Hybrid Concrete Exposed to Peat Water Environment
Geopolymer hybrid concrete is prepared by activating fly ash bottom ash with an alkaline solution and curing with Ordinary Portland Cement (OPC). OPC could be added to the mixture to increase the reaction, promote hydration, and assist in curing at room temperature. Peat water is an acidic organic environment that may reduce the durability of concrete. The purpose of this research is to determine the effect of Portland cement on the properties of FABA geopolymer hybrid concrete exposed to peat water. Portland cement was used in geopolymer as an additive and a substitute. Compressive strength, porosity, and weight change were evaluated for both mixtures. The NaOH molarities were 10, 12, and 14M, the NaOH/sodium silicate ratios were 1.5, 2.0, and 2.5, and the Ordinary Portland Cement percentages were 0, 10, and 15%. Specimens were exposed to peat water for up to 91 days following 28 days of room temperature curing. The geopolymer mixture with 10M NaOH, 2.5M Ms, and 15% OPC had the highest compressive strength and the lowest porosity. The FABA geopolymer hybrid with OPC had a slightly greater compressive strength and a lower porosity than the geopolymer containing OPC as a cement replacement material. In addition, weight change is more stable in geopolymers containing OPC. Based on the performance of both mixes in peat water, it is recommended to use OPC as an additive in FABA geopolymer hybrid concrete.
Herein, mixed–metal nanocomposite catalysts with various compositions (CoFe2O4/xFe2O3; x = 0, 0.25, 0.50, 0.75 and 1) were successfully fabricated by a co–precipitation method. The composition and morphology of the catalyst were systematically characterized. The catalyst with the highest Co content (CoFe2O4), exhibited the greatest efficiency for the acid orange 7 (AO7) degradation via peroxymonosulfate (PMS) activation. The effects of several experimental parameters including pH, CoFe2O4 loading, and PMS dosage on AO7 degradation were studied, and the catalytic activity was found to increase with the mentioned parameters. Moreover, CoFe2O4 displayed adequate reusability and was able to degrade AO7 for at least four consecutive cycles. In addition, the total organic carbon (TOC) removal of CoFe2O4 was determined while the catalyst stability was observed from the metal leaching in the treated solution. Furthermore, the magnetism of CoFe2O4 provides facile separation of the catalyst from the treated solution. Sulfate radicals (SO4•–) were identified as the main reactive species responsible for AO7 degradation.