Journal of King Saud University, Engineering Sciences最新文献

The objective of this research is to investigate different chemical pretreatment methods to reduce the lignin and hemicellulose content of Omani Prosopis Juliflora. The pretreated wood will then be acid hydrolyzed to convert the cellulose content to sugar. Four types of pretreatment methods were employed, namely: Alkaline pretreatment (Method I), Alkaline + Hydrogen peroxide pretreatment (Method II), Alkaline + Hydrogen peroxide + acid-chlorite pretreatment (Method III) and Alkaline + H₂O₂ + Acid-chlorite + bicarbonate pretreatment (Method IV). The effectiveness of each pretreatment method was assessed by measuring lignin, hemicellulose, and cellulose contents and the crystallinity index (CrI) using X-ray diffraction (XRD) analysis. The results were further assessed by taking images of the wood samples after each pretreatment step using Scanning Electron Microscope (SEM). The results showed that the CrI increased from 51% for the untreated samples to 61%, 65%, 68% and 73.2% after treating with Method I, II, III and IV, respectively. Measuring the cellulose, hemicellulose and lignin contents showed that the effectiveness of the methods in ascending order was Method I < Method II < Method III < Method IV.

The pretreated wood samples by method IV were acid hydrolyzed. The effect of acid type, namely: H₂SO₄, HNO₃, HCl and H₃PO₄, concentration and hydrolysis time on the %conversion of cellulose to sugar was investigated. The results revealed that H₂SO₄ was the most effective acid, whereas H₃PO₄ was the weakest. The efficiency of the tested acids follows the following order: H₂SO₄ > HNO₃ > HCL > H₃PO₄. For all acids tested, the %conversion of cellulose to reducing sugar as a function of time increases linearly till t = 90 min, after which no change in the %conversion was obtained. Investigating the effect of acid concentration showed that as the concentration increases, the %conversion increases too. Upon increasing acid concentration from 1% to 10%, the %conversion increases from 12% to 62% for H₂SO₄, from 5% to 43% for HNO₃, from 0% to 47% for HCl, and from 5% to 34% for H₃PO₄.

Global Navigation Satellite System (GNSS) provides ellipsoidal heights, whereas engineering projects need orthometric heights of points. Thus, to take advantage of GNSS in engineering work, the relation between orthometric and ellipsoid height must be determined as a function of position by geoid modeling. The Red Sea coastal cities have various natural potentials that render them economically promising cities that are attractive to numerous investors and visitors alike. Over the past years, there has been an increased governmental awareness of setting up large projects in these cities. With the increasing utilization of GNSS in a number of these projects, there is an imperative need to develop a local geoid model in this region. This study is an attempt to use a geometric method for the study area in order to develop a local geoid model and a local digital elevation model. In addition, the performance of EGM2008, SRTM, and ASTER is evaluated. In order to develop the local geoid model, the polynomial regression method and Artificial Neural network (ANN) technique are employed. Performance evaluation of the studied methods is based on a compilation of various statistical parameters and goodness-of-fit measures, followed by a comparison of methods outputs. The study indicates significant improvements in the local geoid model when using both methods. Additionally, the model resulting from the ANN appears more reliable compared to the calculated model using polynomial regression. In this study, the accuracy of EGM2008 is about ±0.466 m. Moreover, regarding the global digital elevation model, ASTER outperforms SRTM by about ±0.905 m.

In this paper, the performance of hardsurfacing Cobalt alloy (Stellite 6) and Nickel alloy (Colmonoy 88) was tested in tribological slurry conditions by using a pot tester. Thermal spraying powders were deposited on AISI 316L substrates by using a high-velocity oxy-fuel (HVOF) technique. Wear experiments are carried out using a lab-scale pot tester at low velocities like 1.81, 2.71, 3.61, and 4.59 m/s. The high mass flux of ashes (ranging 30–60 wt%) is used to produce severe accelerated conditions. The effect of the size fraction of eroding particles was evaluated by preparing the multi-sized slurries of size fractions (ASTM: −200, −140 + 200, −100 + 140, and −60 + 100). Results show that the microhardness of AISI 316L was improved by the HVOF depositing of Cobalt alloy-6 and Nickel alloy-88. The average surface microhardness of Cobalt alloy-6 was found lower (439 ± 19 HV₁₀₀₀) than the Nickel alloy-88 coating (601 ± 11 HV₁₀₀₀). Erosion performance of coatings was found to be increased with an increase in the value of the velocity, time, mass flux, and weighted mean size of eroding particles. Results show that the Ni-alloy improved the wear resistance of AISI 316L by 2.03 ± 0.021 times in fly ash slurry conditions and 3.21 ± 0.035 times in bottom ash slurry conditions. However, the Co-alloy was beneficial in reducing the wear of AISI 316L by 1.48 ± 0.019 times in fly ash and 2.50 ± 0.032 times in bottom ash slurry conditions. Moreover, the maximum wear of AISI 316L steel was observed at an impingement angle of 30° whereas 60° and 45° for Ni-alloy and Co-alloy coatings respectively in fly ash conditions. Although, the AISI 316L and Ni-alloy coating show maximum wear at the same impingement conditions under the bottom ash slurry conditions. However, the Co-alloy coating showed maximum wear at 60° in bottom ash slurry conditions.

In this study, the main execution activities associated with global roadways construction projects (RCPs) were identified and categorized into five main activities of RCPs as follows: (A) Preliminary Preparations; (B) Earthworks (cut/fill); (C) Implementing of sub-base and base layers; (D) Implementing of bituminous layers and (E) Traffic safety and road furniture. A field survey was conducted, and a comprehensive practical risk checklist consisting of 39 crucial risk factors affecting RCPs activities in Egypt was introduced as a case study. The probability of occurrence and the impacts on RCPs objectives (time, cost, and quality) and the risk severity were determined while the key risk factors were highlighted. The correlations between the risk factors indices were measured, and the strongest relationship was found between time and cost severities. The weights of time and cost percentages of each activity were identified, as well as the expected percentages of time and cost overruns. Activity (B) had the highest percentages of execution time and associated cost among the whole activities, i.e., 31% for time and 29% for cost. While the average overall time and cost overruns were found (at 15–20) % and (10–15) %, respectively. The effect on the quality of each activity and the overall effect on the project’s final quality were also evaluated. The results indicated a high effect on the quality of activities (A), (B), and (D) and a moderate effect on activities (C) and (E). Furthermore, the influence on the overall quality of the entire project was found with a high effect.

In this paper, a Two-Level, Three-Phase, Reduced-Switch (2L3PRS) Voltage Source Converter (VSC) based Distribution Static Synchronous Compensator (DSTATCOM) integrated with a grid-tied solar photo-voltaic (PV) array has been discussed, and its performance investigation has been carried out. A versatile control strategy is proposed, which gives the system maximum power point tracking capability with a stepped perturbation and observation (P&O) algorithm and the grid current is maintained at unity power factor. The layout, in addition to the control technique, helps in supplying active power to the power grid and feeding active and reactive power demand of the 3-phase reactive unbalanced load. Modified Synchronous Reference Frame (MSRF) theory-based current control methodology is implemented to sustain DC-link voltage and to maintain the voltage balancing across split capacitors under all loading conditions. This modified algorithm generates switching pulses for three-phase VSI with only four IGBT switches for fulfilling the desired objectives like maintaining a constant DC link voltage, balancing split-capacitor voltages, balancing the power-sharing between the power grid and the solar-PV energy system, balancing the grid currents and voltages in case of unbalanced loading conditions and maintaining unity power factor operation of the grid by making the D-STATCOM compensate for load reactive power. The proposed system is replicated in MATLAB/Simulink using SimPowerSystems software-based environment. The experimental outcomes have been obtained with a digital real-time simulator to vindicate the simulation results. The experimental, as well as simulation results of the proposed real-time-based model, are demonstrated for three unbalanced single-phase inductive linear loads and with a load on one Phase kept open in the Power Factor Correction (PFC)mode of operation of D-STATCOM.

Waste from low-density polyethylene products after lifespan accounts for 70% of solid waste in most dumpsites, contributing to environmental impacts. Eggshell foul smells are a threat to human and animal health. Before this study, there was no research documentation on transforming both wastes into green composites for engineering applications. This work developed composites using recycled low-density polyethylene (RLDPE) and eggshell Nanoparticles. They were evaluated structurally and mechanically. Straining, which affirms an improvement in the load-bearing capacity of the RLDPE due to the incorporation of eggshell Nanoparticles, was established by the composite XRD peak broadness. Structural integrities of the composites were confirmed with SEM. Maximum tensile strength was noted at 10% eggshell Nanoparticle additions to the RLDPE, equal to a 68% increase. About 52 and 19% enhancements in respective flexural strength and hardness value with a 0.85% reduction in impact energy were noted at 12% eggshell Nanoparticle additions. The probability value, 0.0481 <0.05 established the significance of the mono-variate regression model to estimate the tensile strength of RLDPE/eggshell Nanoparticle composites, and the model has 92.7% confidence. A bumper fascia prototype was fabricated from RLDPE/10% eggshell Nanoparticle composite possessing 10.64 Nmm⁻² tensile strength, 21.964 Nmm⁻² flexural strength, 21.69 J impact energy, and 59 VHN hardness value using sheet forming technique. Therefore, future usage of the developed RLDPE/10% eggshell Nanoparticle composite is established.

The purpose of this paper is to enable members of the construction project team to understand the factors which they must closely monitor to complete the project with the required performance. Therefore, the research aimed to develop an artificial neural network (ANN) model to predict construction project performance based on the above factors.

A group of (34) factors that affect the performance of the project has been identified based on practitioners' opinions. ANN was designed to predict the project performance model using seven inputs that represent six factors that were prioritized as the most influencing factors. The model showed the factors that affect project performance as follows: Coordination and commitment of project parties (30.9%), Schedule estimate (25.4%), Project team experience and availability (24.5 %), and Support from senior management (14.3%).

We concluded to design a model that predicts project performance based on previous influencing factors, as this model has a prediction accuracy of 96.1 % and an error of 3.9 %.

Climatic change and global warming are pushing researchers to develop waste-based alternatives to cement and conventional concrete, which would have low embodied energy and operational energy due to better insulation properties. In this context, the current study presents the production of ultra-lightweight geopolymer foam aggregate utilizing coal fly ash. Fly ash was activated by two alkaline activators, sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃), and Na₂SiO₃ performed as foaming agents as well. Sodium bicarbonate (NaHCO₃) was also used as an additive for geopolymer hardening and early strength gain. A novel curing method, microwave-oven curing, was practiced as an alternative to conventional energy and time-intensive curing techniques to promote rapid strength development and sustainability of materials and technology. The physicomechanical performance (morphology, expansion, density, specific gravity, water absorption, strength against compression, and impact loading) of manufactured aggregates was examined for pertinent use to formulate ultra-lightweight foam concrete, and the properties were also compared with natural as well as synthetic lightweight aggregate. Results indicated that manufactured aggregates experienced physicomechanical properties that would be suitable for designing lightweight concrete both for structural and insulation purposes. Satisfactory results of experimentation also confirmed the potential of microwave-oven curing to replace conventional curing techniques to realize economical, energy-efficient, and eco-efficient manufacturing of artificial aggregate.

Mine tailings stored in the tailings storage facility (TSF) are normally loose and failure-prone for several reasons, such as liquefaction, erosion, overtopping, piping, and high excess pore water pressure (PWP). The investigation of the mechanical behavior of tailings material is essential for engineering design and safety evaluation of the TSF during mining operations, closure, and rehabilitation. As such, laboratory compaction, consolidation, and direct shear strength experiments are carried out on three different fine-grained mine tailings, named coal tailings (CT), red mud (RM), and gold tailings (GT). Compared to CT and RM, GT showed higher dry density at the optimum moisture content (OMC) and lower compressibility. The permeability of GT is similar to RM but much higher than that of CT. CT and GT showed the highest cohesion and angle of internal friction, respectively, among the tested materials. The direct shear test, among all the methods used, provided the highest dry density and lowest void ratio. The final state parameters obtained in compaction, consolidation, and direct shear tests are critically compared, which is the novelty of this study. This research explored useful information on the geotechnical properties of different tailings that can help mining operators and researchers effectively design and manage the tailings in the TSF.