Abstract
High-grade calcium aluminate cement (CAC) has been successfully synthesized from municipal alumina waste and limestone under mild reaction conditions. Mineralogical composition and ...microstructure of the sintered mixes were investigated using X-ray diffraction and FESEM; valuable cementing phases such as CA, CA
2
, and C
12
A
7
were observed in addition to the C
3
A phase that was detected in the mixes with high CaCO
3
content. Mix CA60 containing 60 wt% alumina waste has achieved the best sinterability (less than 1 vol% porosity) and the highest densification (~ 2.65 g/cm
3
bulk density) at 1450 °C. Densification, cold-crushing strength (CCS), and microstructure of the hydrated cement samples (From Mix CA60) were investigated. The cast cement specimens revealed better density and CCS characteristics (63.1 and 74 MPa at 7 and 28 days, respectively) in comparison with the commercial cement. Conventional castables (5 × 5 × 5 cm
3
) were prepared from mixtures composed of 15 wt% cement and 85 wt% aggregates (40% Al
2
O
3
), where CA60 and commercial cement were used to compare the effect of the manufactured CA60 cement with the commercial one. The castables prepared with CA60 cement have shown a higher strength at 110 °C with 4.5 MPa when compared to the commercial CAC at the same temperature (1.8 MPa). Accordingly, this study contributes not only to preserving the environment from the accumulation of industrial wastes but also to valorizing and adding value to these wastes.
Hypertension (HTN) is a primary global health concern. Moreover, according to the 2010 Global Burden of Disease, hypertension accounted for roughly a quarter of cardiovascular disease fatalities and ...1.9 percent of all deaths in Saudi Arabia in 2010. Also, hypertension is a significant risk factor for cardiovascular disease, morbidity, and mortality. However, assessing blood pressure (BP) and preventing hypertension among children and adolescents has become a global priority. This study aims to determine the prevalence of hypertension among children in the Jazan region of Saudi Arabia. Also, to determine the common risk factors associated with pediatric hypertension. We conducted this cross-sectional study among boys and girls aged 6-14 years visiting Al-Rashid Mall, one of the two main malls in Jazan city, the capital of Jazan region, Saudi Arabia, between November 2021 and January 2022. We included children willing to participate in the study after obtaining their parents' consent and children's assent. We used a standardized questionnaire to interview the parents to collect the children's data. We also measured the children's resting BP. Then we classified the measurements according to the updated International Pediatric Hypertension Association (IPHA) chart. We also measured the height and weight of the children and calculated their BMI. We used SPSS version 25 for the data entry and analysis. Our results showed that the prevalence of hypertension and prehypertension was insignificantly higher in females (11.84% and 12.65%) compared to males (11.52% and 11.52%), respectively. Our participants' main associated factors with prehypertension and hypertension were overweight, obesity, and family income. Pediatric hypertension and prehypertension were highly prevalent in Jazan region. Therefore, being overweight and obese should be considered risk factors for pediatric hypertension. Our study emphasizes the need for early intervention to prevent pediatric HTN, particularly among overweight and obese children.
To provide efficient networking services at the edge of Internet-of-Vehicles (IoV), Software-Defined Vehicular Network (SDVN) has been a promising technology to enable intelligent data exchange ...without giving additional duties to the resource constrained vehicles. Compared with conventional centralized SDVNs, hybrid SDVNs combine the centralized control of SDVNs and self-organized distributed routing of Vehicular Ad-hoc NETworks (VANETs) to mitigate the burden on the central controller caused by the frequent uplink and downlink transmissions. Although a wide variety of routing protocols have been developed, existing protocols are designed for specific scenarios without considering flexibility and adaptivity in dynamic vehicular networks. To address this problem, we propose an efficient online sequential learning-based adaptive routing scheme, namely, Penicillium reproduction-based Online Learning Adaptive Routing scheme (POLAR) for hybrid SDVNs. By utilizing the computational power of edge servers, this scheme can dynamically select a routing strategy for a specific traffic scenario by learning the pattern from network traffic. Firstly, this paper applies Geohash to divide the large geographical area into multiple grids, which facilitates the collection and processing of real-time traffic data for regional management in controller. Secondly, a new Penicillium Reproduction Algorithm (PRA) with outstanding optimization capabilities is designed to improve the learning effectiveness of Online Sequential Extreme Learning Machine (OS-ELM). Finally, POLAR is deployed in control plane to generate decision-making model (i.e., routing policy). Based on the real-time featured data, this scheme can choose the optimal routing strategy for a specific area. Extensive simulation results show that POLAR is superior to a single traditional routing protocol in terms of packet delivery ratio and latency.
Thermal treatment is applied for the direct conversion of palm stalk waste to Fe3O4 (np)@carbon sheets (Fe3O4 (np)@CSs). The effect of conversion temperature was investigated. The TEM examination of ...the prepared magnetic Fe3O4 (np)@CSs showed the formation of Fe3O4 (np) in a matrix of carbon sheets as a coated layer with surface functional groups including carbonyl and hydroxyl groups. Removal of dyes such as methyl orange, methylene blue, and neutral red was achieved using fabricated Fe3O4 (np)@CSs which were prepared at 250 °C, 400 °C, and 700 °C in a weak acidic medium. By studying the contact time effect for the adsorption of methylene blue, neutral red, and methyl orange, using the fabricated Fe3O4 (np)@CSs which were prepared at 250 °C and 400 °C, equilibrium occurred between 120 min and 180 min. In addition, the first-order and second-order kinetic models were applied to the adsorption data. The results revealed that the adsorption data fit better with the second-order kinetic model. Furthermore, the Freundlich model was found to be more suitable for describing the process of the separation of the dyes onto Fe3O4 (np)@CSs which were prepared at 250 °C and 400 °C, suggesting heterogenous surfaces and multi-layer adsorption.
We present a generalised phase field-based formulation for predicting fatigue crack growth in metals. The theoretical framework aims at covering a wide range of material behaviour. Different fatigue ...degradation functions are considered and their influence is benchmarked against experiments. The phase field constitutive theory accommodates the so-called AT1, AT2 and phase field-cohesive zone (PF-CZM) models. In regards to material deformation, both non-linear kinematic and isotropic hardening are considered, as well as the combination of the two. Moreover, a monolithic solution scheme based on quasi-Newton algorithms is presented and shown to significantly outperform staggered approaches. The potential of the computational framework is demonstrated by investigating several 2D and 3D boundary value problems of particular interest. Constitutive and numerical choices are compared and insight is gained into their differences and similarities. The framework enables predicting fatigue crack growth in arbitrary geometries and for materials exhibiting complex (cyclic) deformation and damage responses. The finite element code developed is made freely available at www.empaneda.com/codes.
•We present a generalised, phase field-based fatigue model for elasto-plastic solids.•Cyclic deformation is modelled by a combined non-linear kinematic/isotropic hardening law.•Three classes of phase field models are considered: AT1, AT2 and PF-CZM.•A quasi-Newton algorithm is used to enable a robust and efficient monolithic scheme.•The potential of the model is showcased with paradigmatic 2D and 3D case studies.
The high conversion efficiency has made metal halide perovskite solar cells a real breakthrough in thin film photovoltaic technology in recent years. Here, we introduce a straightforward strategy to ...reduce the level of electronic defects present at the interface between the perovskite film and the hole transport layer by treating the perovskite surface with different types of ammonium salts, namely ethylammonium, imidazolium and guanidinium iodide. We use a triple cation perovskite formulation containing primarily formamidinium and small amounts of cesium and methylammonium. We find that this treatment boosts the power conversion efficiency from 20.5% for the control to 22.3%, 22.1%, and 21.0% for the devices treated with ethylammonium, imidazolium and guanidinium iodide, respectively. Best performing devices showed a loss in efficiency of only 5% under full sunlight intensity with maximum power tracking for 550 h. We apply 2D- solid-state NMR to unravel the atomic-level mechanism of this passivation effect.
In this paper, nanostructured hematite p-CaFe2O4/n-Fe2O3 heterojunction photoanodes have been fabricated employing a facile template-less film processing technique by controlling the chemical bath. ...Anisotropic growth of a β-FeOOH akaganeite film on FTO conductive glass from an aqueous FeCl3 solution containing CaCl2 followed by a two-step thermal annealing at 550 and 800 °C induces the formation of a p-CaFe2O4/n-Fe2O3 heterojunction. The structural, morphological, electronic states, and electrochemical characteristics of the films have been investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and impedance spectroscopy, respectively. The heterojunction photoanode showed 100% higher photocurrent response than that obtained using a bare hematite electrode under simulated 1-sun illumination (100 mW/cm2). The photocurrent enhancement is attributed to the enhanced charge carrier separation and the reduced resistance in the charge transfer across the electrode and the electrolyte as revealed by electrochemical impedance spectroscopy analysis. The modification of the p-CaFe2O4/n-Fe2O3 heterojunction photoanode with CoPi cocatalyst further facilitates the electron transfer at the electrode/electrolyte interface and thus enhances the photoelectrochemical water oxidation. Since cheap and abundant materials have been employed for the synthesis of the heterojunction photoanode via a simple route, the current results have great importance, both from a scientific and an economical point of view.
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