Journal of King Saud University, Engineering Sciences最新文献

Due to the increase in human population, there is an ever-increasing demand for energy in different sectors which leads to environmental problems like climate change, rise in temperature, and global catastrophes. Cooling systems have become a very essential element in recent decades for mankind. The present system focuses on the design and fabrication of a counter-flow humidification setup which uses biomass-based charcoal as the packing material. Air velocity and water flow rate have been varied along with the density of charcoal. Output parameters such as a change in pressure (ΔP), Coefficient of performance (COP), evaporation rate (ER), humidification efficiency (HE), specific cooling capacity (SCC), and energy consumption (EC) are evaluated. Performance parameters obtained for charcoal are compared with that of standard Celdek Packing. Through experiments, it is found that humidification efficiencies for Celdek and charcoal packing are 77.45% and 57.40% respectively. The overall coefficient of performance obtained is 1.41 for charcoal and 3.17 for Celdek packing. Among the three densities which were considered, charcoal packing with a density of 400 kg/m³ exhibited higher performance with respect to COP, HE, ER, and SCC. Similarly, a water flow rate of 0.4 lpm gave a maximum performance and 0.7 lpm gave the least. It is concluded that charcoal can be considered one of the highly efficient biomass-based materials contributing to sustainable energy related to cooling applications.

Peak ground acceleration ($\mathrm{PGA}$) is one of the critical factors that affect the determination of earthquake intensity. PGA is generally utilized to describe ground motion in a particular zone and is able to efficiently predict the parameters of site ground motion for the design of engineering structures. Therefore, novel models are developed to forecast PGA in the case of the Iraqi database, which utilizes the particle swarm optimization ($\mathrm{PSO}$) approach. A data set of 187 historical ground-motion recordings in Iraq’s tectonic regions was used to build the explicit proposed models. The proposed PGA models relate to different seismic parameters, including the magnitude of the earthquake ($M_w$), average shear-wave velocity ($V_{S30}$), focal depth ($\mathrm{FD}$), and nearest epicenter distance ($R_{\mathrm{EPi}}$) to a seismic station. The derived PGA models are remarkably simple and straightforward and can be used reliably for pre-design purposes. The proposed $\mathrm{PGA}$ models (i.e., models I and II) obtained via the explicit formula produced using the $\mathrm{PSO}$ method are highly correlated to the actual $\mathrm{PGA}$ records owing to low coefficients of variation ($\mathrm{CoV}$) of approximately 2.12% and 2.06%, and mean values (i.e., close to 1.0) of approximately 1.005 and 1.004. Lastly, high-frequency, low absolute relative error ($\mathrm{ARE}$), which is below 5%, is recorded for the proposed models, thereby showing an acceptable error distribution.

In a multi-layered shielding material, the sequence of the arrangement of the layers affects the extent of insulation to acoustic waves. In the current work, hybrid composite laminates have been taken up comprising 10 sequences, employing metallic faceplate (AA6061), paperboard, ballistic-grade aramid, and ultra-high molecular weight polyethylene (UHMWPE) fabrics with an epoxy binder. In the theoretical studies, an analytical model for the transmission loss function has been developed by incorporating the multiple wave reflection principle in combination with interface-wise acoustic impedance grading. The analytical model has been validated using the transmission loss functions from numerical and experimental studies on the different sequences. The numerical simulation has been carried out using the harmonic acoustic analysis module, on Ansys R19.0. The experimentation has been carried out on an impedance tube. The results from the analytical model are in good agreement with the experimental and numerical simulation results, the analytical model can be used for predicting the transmission losses of composite laminates.

Low density polyethylene (LDPE) based water sachet films were recycled into polymer powder by thermochemical treatment. Varying weights of sachet films were dissolved in automotive gas oil (AGO) at elevated temperature, followed by quenching in an ice-bath stainless steel container to determine optimum powder yield and particle size distribution. Sieve analysis of powder was carried out into different particle sizes and consequently to eliminate lumps. The polymer powder was subsequently mixed with maleic anhydride treated African mahogany wood dust (WD), in ratios 80:20, 70:30 and 60:40 wt%, and compacted by hot pressing to produce composite samples. Performance evaluation was carried out on the composite using tensile, flexural and impact energy testing techniques. Water absorption test was also carried out to determine hydrophilicity of the composite. The mass of powder yield from thermochemical treatment was about twice the amount of sachet films. Film dissolution of 100 mg/L of AGO gave optimal powder yield and size distribution with minimal lumps. Performance tests showed that, tensile and flexural strength, and impact energy of composites decreased with increase in the weight percent of wood dust. The water absorption test also revealed increased hydrophilicity of the composite with wood dust ratio.

In this work, the adsorption capacity of the biochar obtained from Pinus patula biomass micro-gasification was studied using malachite green (MG) as the probe pollutant. For this purpose, the biomass type (wood pellets and chips) was selected to produce two kinds of biochar (BC). Afterwards, the effects of the adsorbent dose (6, 9 and 12 g/L), the solution pH (4, 7 and 10) and the BC particle size distribution (150–300, 300–450 and 450–600 $\mu$m) for the maximization of the MG retention by the selected BC were evaluated using a faced-centered central composite design, as response surface methodology. The results indicated that the BC derived from wood chips (BWC) exhibited a higher MG dye adsorption capacity than the BC obtained from the wood pellets (BWP) gasification under the same operating conditions after having reached the equilibrium. A second-order regression model was built for describing the MG adsorption behaviour by BWC under the considered experimental domain. The model, which was validated, resulted to be statistically significant and suitable to represent the MG adsorption by the studied BC with a p-value of 0.00 and a correlation coefficient (R²) of 95.59%. Additionally, a three-dimensional response surface graph and a contour plot were utilized to analyze the interaction effects between the factors influencing the adsorption system and to discern the optimal operating conditions for the use of BWC. The maximal MG dye retention (99.70%) was found to be at an adsorbent dose, pH solution and a particle size distribution of 9.80 g/L, 10 and from 150 to 300 $\mu$m, respectively. Therefore, the BWC tested can be utilized for the treatment of water polluted with dyes, contributing to the establishment of a circular economy.

This paper presents our research efforts in the discovery of pioneering synthetic routes and designing low molecular-weight maleic-anhydride (MA) homopolymers and MA-n-octyl acrylamide (AAO) copolymers (YMR-series) and their application as scale inhibitors for mineral scales. Hence, the solvent-free, eco-friendly, rapid microwave-assisted method has been developed for the first time to synthesize these antiscalants with higher yield and better efficiency. The inhibition ability on the CaSO₄ and CaCO₃ scale is 100 % with a 3 ppm dosage level at pH 10.45 and temperature 70 °C.

Morphological changes of the CaCO₃ and CaSO₄ scales due to the strong inhibition action of YMR-series polymers have been studied by scanning electronic microscopy (SEM) and X-ray powder diffraction (XRD) analysis. It is also observed that the anti-scaling effect of the polymers greatly depends on the molecular weight, while MA copolymers show better inhibition efficiency compared to MA homopolymers.

Air conditioning (AC) is a key driver to produce electricity consumption, particularly in residential buildings. In Indonesia, the electricity bill during pandemic covid-19 has increased to a high level on hot days. This is because during these periods many consumers applied their AC for a long time at the same time. It is therefore essential to develop an innovative model to control the electricity peak price and keep a comfortable room during hot days. Many previous studies have confirmed that applied evaporative cooling or other technologies can minimize the whole consumption and cost. This research aims to design a pre-cooling model (PM) for AC to avoid high electricity prices at midday during hot days. To achieve this goal a mathematical model was developed to define the energy cost (EC) and total cost (TC) for AC during the hot season. Under numerical optimization, the EC can be minimized when a spike may occur due to increased temperature at midday for a half hour (0.5 h) and one hour (1 h) spike cases. To justify this model, a PM was applied for two different building characteristics. As a result, the benefits of a PM if a spike occurs for 0.5 h and 1 h were achieved, such as IDR 10,061 (30.43 %) and IDR 10,693 (24.44 %) for building-1; IDR 12,071 (37.40 %) and IDR 14,844 (34.97 %) for building-2. In addition, the TC considering the probability of a spike of 0.5 h and 1 h if the spike occurs every five minutes were IDR 45,247 and IDR 38,287 for building-1 and building-2, respectively.

The current research aims to study the suitability of Damietta branch meanders for safe first-class cargo transportation. This branch is the River Nile eastern waterway bifurcated at the beginning of the Delta region, which is about 22.0 km downstream of El-Roda gauge in Cairo. It extends for 244 km to the Mediterranean Sea. The branch plan form was examined for meanders. Fifty-one meanders could be identified throughout. Their characteristics were analyzed. The results revealed the existence of eight sharp meanders and seven critical looping ones that would slow down and jeopardize the first-class navigation traffic. Also, it was found that about 68 % of the looping meander lengths could be saved if cut-offs were executed. Accordingly, examples of straightening the river at four meanders were proposed for clarification. It was found that their lengths could be reduced by 51.10 %. Finally, the study concluded that in order for the Damietta branch to be qualified and entitled to safe first-class cargo transportation, the sharp meanders and critical loops have to be subject to training works and re-channelized.

This paper focuses on the investigation of fresh, mechanical, and durability properties of concrete with the influence of fly ash and polypropylene fiber. In this study, cement was partially replaced by 15 % and 30 % fly ash content in weight, whereas polypropylene fiber was incorporated in concrete mixes at 0.06 %, 0.12 %, and 0.18 % by volume. Twelve concrete mix proportions were developed, and slump, density, ball penetration, and compacting factor tests were conducted to examine the fresh concrete properties. Besides, mechanical characteristics, including the uniaxial compressive and splitting tensile strength of concrete, were evaluated at 7, 28, and 90 days. Further tests of concrete durability, including rapid chloride permeability test, sorptivity, and water penetration, were performed at 90 days. The results exhibited that the incorporation of fly ash developed fresh concrete properties, while polypropylene fiber decreased the fresh characteristics of concrete. Furthermore, the combination of fly ash and polypropylene fiber in concrete was substantially attained to improve the mechanical and durability characteristics compared to the control mix. Mix proportion of 15 % fly ash and 0.12 % polypropylene fiber exhibited a pronounced influence on compressive strength, chloride permeability, sorptivity, and water penetration compared to other concrete mixtures.

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.