Effect of Superplasticizer Dosage on Compressive Strength and Microstructure of High Volume Basic-Oxygen Slag Mortar Exposed to Sea Water Attacks

The influence of superplasticizer addition on durability reinforcement of cement mortars made with basic-oxygen blast-furnace slag fine aggregate (BOF) as completely substitute for natural sand after being exposed to sea water solution for 6 months was evaluated by determining physico-mechanical characteristics in terms of water absorption and compressive strength in addition to microstructure analysis. In this procedure, all studied mixtures were doped with 1% and 2% superplasticizer. After the initial curing of samples in tap water for 28 days, they were subjected to sea water solution for 6 months using water to binder ratios of 0.35 and 0.45. The new hydration phases and microstructure of hardened specimens were identified by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The results showed that cement mortars with slag fine aggregate blended with 2% SP offered better water absorption, compressive strength and microstructure than their counterparts with natural sand against sea water attacks. Therefore, they can be used in offshore structure applications

Hydration Characteristics of Limestone Filled Cement Pastes

The physico-mechanical properties of hardened limestone-filled cement pastes were studied. Five filled-cements were prepared from 0, 5, 10, 15 and 20 wt. % of limestone and OPC. The water of consistency of filled-cement pastes was 0.275, 0.275, 0.275, 0.272, and 0.270, respectively. The pastes are moulded into one inch cubic moulds and left within the moulds at 100% relative humidity for 24 h, then demoulded and cured under tap water for 3, 7, 28, and 90 days. At each hydration time, the combined water, bulk density, total porosity and compressive strength of the hardened filled-cement pastes were determined. Some selected filled-cement pastes were investigated using differential thermal analysis (DTA) and scanning electron microscope (SEM) Techniques. Addition of limestone to Portland cement causes an increase of hydration at early ages inducing a high early strength, but it can reduce the later strength due to the dilution effect. The results indicate that the addition of limestone up to 5 wt. % improves the physico-mechanical properties of ordinary Portland cement which acts as a nucleating agent and accelerates the hydration of filled cement pastes. The addition of 5 wt. % limestone can be used in the production of portland cement according to the international specifications. On the other side, the addition of 10-20 wt. % limestone can be used in the production of blended or mixed cements

Investigation of the Effect of Zn Ions Concentration on DC Conductivity and Curie Temperature of Ni-spinel Ferrite

The mixed polycrystalline ferrites Ni1-sZnsFe2O4, were obtained using the standard double sintering technique by mixing high purity of metal oxides NiO, ZnO and Fe2O3 for different concentration of Zn ion. DC electric properties and inductance of the prepared samples were carried out over the temperature range of 300 up to 773 K using two probe method and LCR meter. The thermal dependence of DC electrical conductivity (σDC) for the mixed Ni-Zn spinel ferrites with different Zn concentrations was investigated. In general, σDC found to be increased with both increasing temperature and Zn content. The thermal measurement of σDC confirmed the semiconductor behavior for Zn substituted Ni spinel ferrites and follows Arrhenius relation in the investigated temperature region. The variation of σDC indicated that the conduction mechanism was correlated to a small polaron-hopping. The activation energies of both regions, ferrimagnetic (Ef) and paramagnetic (Ep) and △E=Ep-Ef for all studied compositions were estimated. The calculated activation energy in the ferrimagnetic region was found to be less than that in paramagnetic region. The influenced of increased Zn ions on σDCand activation energies was investigated. From these results, it is found that △E and σDC decrease with increasing of Zn content. The inductance measurements for the prepared samples show constant values at low temperature range up to Curie temperature (TC), then the inductance decrease sharply except for ZnFe2O4 which confirmed that it is a paramagnetic at room temperature. The Curie temperature was determined from σDC and inductance measurement, which was found to be nearly the same and they decreased with increasing of Zn ions. The experimental results reveal that the electric properties and inductance, which can be dramatically changed by substitution of the non-magnetic Zn ions in Ni spinel ferrite. These improved properties of the mixed Ni-Zn spinel ferrite suggest uses as a soft ferrite material, which is proved an interest material for technological and scientific applications.The mixed polycrystalline ferrites Ni1-sZnsFe2O4, were obtained using the standard double sintering technique by mixing high purity of metal oxides NiO, ZnO and Fe2O3 for different concentration of Zn ion. DC electric properties and inductance of the prepared samples were carried out over the temperature range of 300 up to 773 K using two probe method and LCR meter. The thermal dependence of DC electrical conductivity (σDC) for the mixed Ni-Zn spinel ferrites with different Zn concentrations was investigated. In general, σDC found to be increased with both increasing temperature and Zn content. The thermal measurement of σDC confirmed the semiconductor behavior for Zn substituted Ni spinel ferrites and follows Arrhenius relation in the investigated temperature region. The variation of σDC indicated that the conduction mechanism was correlated to a small polaron-hopping. The activation energies of both regions, ferrimagnetic (Ef) and paramagnetic (Ep) and △E=Ep-Ef for all studied compositions were estimated. The calculated activation energy in the ferrimagnetic region was found to be less than that in paramagnetic region. The influenced of increased Zn ions on σDCand activation energies was investigated. From these results, it is found that △E and σDC decrease with increasing of Zn content. The inductance measurements for the prepared samples show constant values at low temperature range up to Curie temperature (TC), then the inductance decrease sharply except for ZnFe2O4 which confirmed that it is a paramagnetic at room temperature. The Curie temperature was determined from σDC and inductance measurement, which was found to be nearly the same and they decreased with increasing of Zn ions. The experimental results reveal that the electric properties and inductance, which can be dramatically changed by substitution of the non-magnetic Zn ions in Ni spinel ferrite. These improved properties of the mixed Ni-Zn spinel ferrite suggest uses as a soft ferrite material, which is proved an interest material for technological and scientific applications

FT-IR Studies of Nickel Substituted Polycrystalline Zinc Spinel Ferrites for Structural and Vibrational Investigations

FT-IR spectra of Ni1-sZnsFe2O4 spinel ferrite, s changed by 0.2 according to 0.0 s 1.0, have been analyzed in the frequency range (350−1000) cm-1. Six polycrystalline ferrites samples were synthesized using the conventional standard double sintering ceramic method. Two main absorption bands were observed, their positions were found to be strongly dependent on s-value. The high frequency band in the range 550-600 cm−1 and a low frequency band at around 400 cm−1 were assigned to tetrahedral Td and octahedral Oh sites, respectively, of spinel lattice. Force constant (FC) was calculated for Tdand Oh sites and was found to decrease with increasing Zn ions. Threshold frequency nth for the electronic transition was determined and found to increase with increasing Zn ions. Cations distribution for the prepared mixed ferrite was concluded based on the FT-IR spectra. The ionic radii for each site were correlated to the cations distribution of the given ferrite.FT-IR spectra of Ni1-sZnsFe2O4 spinel ferrite, s changed by 0.2 according to 0.0 s 1.0, have been analyzed in the frequency range (350−1000) cm-1. Six polycrystalline ferrites samples were synthesized using the conventional standard double sintering ceramic method. Two main absorption bands were observed, their positions were found to be strongly dependent on s-value. The high frequency band in the range 550-600 cm−1 and a low frequency band at around 400 cm−1 were assigned to tetrahedral Td and octahedral Oh sites, respectively, of spinel lattice. Force constant (FC) was calculated for Tdand Oh sites and was found to decrease with increasing Zn ions. Threshold frequency nth for the electronic transition was determined and found to increase with increasing Zn ions. Cations distribution for the prepared mixed ferrite was concluded based on the FT-IR spectra. The ionic radii for each site were correlated to the cations distribution of the given ferrite

Synthetize and Magnetic Properties of Ni Substituted Polycrystalline Zn-spinel Ferrites

The mixed polycrystalline Ni1-sZnsFe2O4 ferrites where s is the percentage increments of Zn ions, were prepared using the standard double sintering by mixing pure metal oxides NiO, ZnO and Fe2O3. The netmagnetization (Mnet)was studied at room temperature as a function of applied magnetic field(H)over the range of (0-45) Oe ina constant magnetizing frequency (ν = 50 Hz). Mnet show increasing with increasing of H. Mnet is found to increase for the samples of s= 0.0, 0.2, 0.4 and 0.6 then decreases there after while the concentration of Zn increases in matrix i.e. samples of s = 0.8 and 1.0. The increasing of the magnetization with increasing of Zn+2 ions for the samples of s= 0.0, 0.2 and 0.4 explained by Neel’s two-sublattice model. However,for the decreasing of magnetization beyond > 0.6 explained by Yafet and Kittel for the three-sublattice model. The Yafet-Kittel angle (YK) for the samples of s = 0.4 to s = 1.0, shows increasing with increasing of the amount of nonmagnetic ions Zn+2 in ferrite. The relation between H and relative permeability (µr) show an interesting behavior of the present ferrite samples. µr for the samples of s = 0.0, 0.2, 0.8 and 1.0 is found to be smaller than the samples with s= 0.4 and s= 0.6. Substitution of the non-magnetic Zn+2 ions in Ni spinel ferrite has a tremendous influence such the magnetic properties. Furthermore, Zn content has significant influence on the magnetic properties for Ni ferrites, so, the mixed Ni-Zn spinel ferrite is considered a soft ferrite material, which is proved an interesting material for technological and scientific applications.The mixed polycrystalline Ni1-sZnsFe2O4 ferrites where s is the percentage increments of Zn ions, were prepared using the standard double sintering by mixing pure metal oxides NiO, ZnO and Fe2O3. The netmagnetization (Mnet)was studied at room temperature as a function of applied magnetic field(H)over the range of (0-45) Oe ina constant magnetizing frequency (ν = 50 Hz). Mnet show increasing with increasing of H. Mnet is found to increase for the samples of s= 0.0, 0.2, 0.4 and 0.6 then decreases there after while the concentration of Zn increases in matrix i.e. samples of s = 0.8 and 1.0. The increasing of the magnetization with increasing of Zn+2 ions for the samples of s= 0.0, 0.2 and 0.4 explained by Neel’s two-sublattice model. However,for the decreasing of magnetization beyond > 0.6 explained by Yafet and Kittel for the three-sublattice model. The Yafet-Kittel angle (YK) for the samples of s = 0.4 to s = 1.0, shows increasing with increasing of the amount of nonmagnetic ions Zn+2 in ferrite. The relation between H and relative permeability (µr) show an interesting behavior of the present ferrite samples. µr for the samples of s = 0.0, 0.2, 0.8 and 1.0 is found to be smaller than the samples with s= 0.4 and s= 0.6. Substitution of the non-magnetic Zn+2 ions in Ni spinel ferrite has a tremendous influence such the magnetic properties. Furthermore, Zn content has significant influence on the magnetic properties for Ni ferrites, so, the mixed Ni-Zn spinel ferrite is considered a soft ferrite material, which is proved an interesting material for technological and scientific applications

Decreasing maize production-consumption gap by intercropping with upland rice using different planting densities under deficit irrigation

A two-year field experiment was conducted in 2018 and 2019 at Gemmiza Agricultural Research Station (Lat. 31.03° N, Long. 30.88° E, 8 m a.s.l.); Gharbia Governorate; Egypt. The aim was to use untraditional sowing method to intercrop maize with upland rice using three maize planting densities (25, 37.5 and 50% of its recommended density) and application of two deficit irrigation treatments (irrigation every 9 and 12 days), in addition to irrigation every 6 days (control) and to study its effect on the yield of both intercrops, competitive relationships and farmer’s income. The results indicated that the highest value of rice yield and its components were found under irrigation every 6 days and 25% maize planting density intercropped with rice. Whereas, the highest value of maize yield and its components were found under irrigation every 9 days and 50% maize planting density intercropped with rice, which also obtained the highest land and water equivalent ratios, area time equivalent ratio, and land equivalent coefficient. Furthermore, the highest total income and monetary advantage index were obtained under irrigation every 9 days and 50% maize planting density intercropped with rice. Thus, these results implied that intercropping maize with upland rice can solve part of the maize production-consumption gap through increasing its production without using additional lands or water.  Keywords: Land and water equivalent ratios, percentage of land saved, area time equivalent ratio, land equivalent coefficient, monetary advantage index, Rice, Maize, Egyp

Kinetic modelling of methanol synthesis over commercial catalysts: A critical assessment

Kinetic modelling of methanol synthesis over commercial catalysts is of high importance for reactor and process design. Literature kinetic models were implemented and systematically discussed against a newly developed kinetic model based on published kinetic data. Deviations in the sensitivities of the kinetic models were explained by means of the experimentally covered parameter range. The simulation results proved that an extrapolation of the working range of the kinetic models can lead towards significant simulation errors especially with regard to pressure, stoichiometric number and CO/CO$_{2}$-ratio considerably limiting the applicability of kinetic models frequently applied in scientific literature. Therefore, the validated data range for kinetic models should be considered when detailed reactor simulations are carried out. With regard to Power-to-Methanol processes special attention should be drawn towards the rate limiting effect of water at high CO$_{2}$ contents in the syngas. Moreover, it was shown that kinetic models based on data measured over outdated catalysts show significantly lower activity than those derived from state-of-the-art catalysts and should therefore be applied with caution for reactor and process simulations. The plausible behavior of the herein proposed kinetic model was demonstrated by a systematic comparison towards established kinetic approaches within both, an ideal kinetic reactor and an industrial steam cooled tubular reactor. Relative to the state-of-the-art kinetic models it was proven that the herein proposed kinetic model can be applied over the complete industrially relevant working range for methanol synthesis

Validation of the Arabic version of the Social Communication Questionnaire

Validated screening and diagnostic tools for autism spectrum disorder for use in Arabic-speaking individuals are scarce. This study validated the Arabic version of the Social Communication Questionnaire. The total study sample included 206 children with autism spectrum disorder and 206 typically developing children (73.8% male; mean age: 8.5 (standard deviation = 2.6) years). The mean Social Communication Questionnaire total score was significantly higher in autism spectrum disorder children than in typically developing children (p < 0.0001). Scores on the three Social Communication Questionnaire subscales also differed significantly between the groups (p < 0.001). Of the 39 items, 37 were endorsed significantly more often in the autism spectrum disorder group. The total Social Communication Questionnaire score did not vary by age or gender. Internal consistency was excellent (alpha = 0.92). In the receiver operating characteristic analysis, the area under the curve for the total score showed excellent discrimination between autism spectrum disorder and typically developing children (area under the curve = 0.95; 95% confidence interval: 0.93–0.97). The areas under the curve for the scale subscores were 0.923 (95% confidence interval: 0.898–0.949) for the social interaction score, 0.872 (95% confidence interval: 0.838–0.905) for the communication score, and 0.856 (95% confidence interval: 0.819–0.893) for the repetitive behaviors score. The findings support the use of the Arabic Social Communication Questionnaire to successfully differentiate children with clinically diagnosed autism spectrum disorder using the established cutoff value for the English version.The authors would like to thank all the staff of the autism centers and schools who contributed in distributing and collecting the SCQ forms. They also would like to thank Western Psychological Services (WPS) staff for their help during the process of translating and reviewing the Arabic SCQ. They acknowledge Jennifer Holmes, ELS, for medical editing. The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The study was funded by the Qatar National Research Fund (NPRP 6-093-3-024)