Journal of King Saud University, Engineering Sciences最新文献

In this paper, a new topology with two shunts flexible AC transmission system (FACTs) devices, thyristor binary switched capacitors (TBSC), and thyristor binary switched reactors (TBSR) based SVC has been developed, which are working in parallel. Both TBSC and TBSR are designed, and simulation results are obtained for the dynamic loading condition. Switching of capacitor and reactor banks with thyristor as a switch is obtained at transient-free conditions so that the significant problem of switching harmonics is eliminated. The coarse control of reactive power is obtained by selecting switchable capacitor banks in binary mode. For fine control, the TBSR bank is designed with a total value equal to the lowest step value of the TBSC bank. It is discrete stepwise compensation at a period of one cycle, and this reactive power compensation is almost continuous as per requirement. It has near-to-zero switchings and zero steady-state harmonics. The mathematical model of TBSC + TBSR has been identified with the system identification toolbox. Different control strategies are implemented as PID controller, Model predictive control, and Model reference adaptive control. The proposed SVC topology performance is discussed based on the performance parameters such as rise time, settling time, and peak overshoot using adaptive controllers.

In recent years, there has been a growth of interest in the development of micro-hydropower power generation, especially in the low-head turbine. Low-head turbines gained popularity due to their high efficiency, relatively low cost, ability to operate at a low flow rate, and low environmental impact. In this aspect, the Archimedes Screw Turbine (AST) could be the primary key to electrifying the rural area in Sarawak, Malaysia, which is surrounded by rivers. This study starts with a conceptual design based on literature review findings. Eventually, the small-scale prototype is then being built and tested in the laboratory. The experiment is set up to simulate the actual Sarawak river velocity to determine the relationship between key performance variables such as the inclination angle of AST and water flow velocity. The findings revealed that the 45° angle of inclination was the optimum angle of AST within the water velocity of 1.0 m/s until 1.5 m/s. At this angle, the highest revolution per minute (RPM) generated by the AST shaft was 179.8, and the highest torque recorded was 0.9Nm. The results were validated through statistical means. It was found that both angles of inclination and river water velocity are significant to RPM and torque generation (p < 0.05). Two statistical models were generated based on linear regression to explain the contribution of water velocity and angle of inclination as inputs to torque and RPM as outputs, with a Pearson R² value of more than 60%. The maximum mechanical power generated is about 1.54 kW, with a maximum efficiency of 94.6%. The outcome of this study would be useful for designing a small-scale AST power generation system by utilizing a low-flow river (velocity < 1.5 m/s) as a power source. This study would contribute to the existing knowledge stock of small-scale AST, primarily to operate in low-flow velocity rivers. For the future study, it is recommended for conducting a pilot study to test the actual performance of AST in the Sarawak River or rivers with similar flow characteristics.

This review intends to discuss on greywater treatment technologies, which are the physiochemical, biological and advanced oxidation process (AOP) treatment technologies that are used to remove organic, nutrient and surfactant pollutants in greywater. The focus of this study is to compare the treatment technologies to remove greywater pollutants in the coastal area. Each technology will be compared in terms of its advantages and disadvantages, including its potential in greywater treatment technologies development. Measurement parameters of water quality from other studies include physicochemical, organic content, nutrient, and surfactant that are developed from each greywater treatment mode. AOP has a huge potential in greywater treatment since the technology has a low cost of development, easy to install, and is able to be deployed on a small scale. The AOP could be combined with other treatment techniques to produce an improved output.

The outer shell of the bulletproof fabric is one of the important parts that help the shield in performing its function of protection in the best way. In this paper, there are two types of high-performance materials used as the outer shell and finished with knife coating with fluorocarbon and polyurethane coating to improve the performance of the two materials. Five laboratory tests were conducted for both materials to show their functional performance efficiency, the ballistic test was applied using two types of calibers 7.62x54MSC and 7.62x54API. A scanning electron microscope was conducted to show the coating effect on samples. Paired sample T-tests were used to show the differences between variables. An improvement was shown in the performance for both ballistic nylon and Cordura after treatment. Finally cordura is more durable, as it recorded the highest value in Puncture test and less damaged, while ballistic nylon recorded the highest value in the abrasion resistance after the same treatment.

The nonlinear free vibration of a porter governor was investigated using an equivalent oscillator model (EOM). The equivalent oscillator model, whose exact periodic solution was derived in terms of the complete elliptic integral of the second kind, was formulated based on quasi-static equilibrium conditions. The derived equivalent oscillator constants for the porter governor were found to be dependent on the maximum potential energy and restoring force of the governor. Simulations of the derived approximate solution for the frequency-amplitude response of the porter governor were found to be in good agreement with corresponding numerical solutions. Investigations showed that the frequency of oscillation of the porter governor decreases with increase in the ball-sleeve mass ratio, rotational speed of the governor and/or arm length.

Eggshell concrete is an innovative green material that helps to recycle eggshell waste while reducing the environmental harm caused by excessive cement production. However, recent studies on eggshell concrete are limited, and the outcomes may vary due to the variation of mix design. The design of the experiment is used to simplify and optimize the study of sustainable concrete, yet analysis involving eggshell concrete is still scarce. This paper aimed to develop mathematical models for the prediction of eggshell concrete compressive strength using mixed regression (MR) and response surface methodology (RSM). Overall, 43 datasets were collected from available studies in the literature on eggshell powder as partial cement replacement. The input variables used were the percentage of eggshell, percentage of Ground Granulated Blast-furnace Slag (GGBS), cement content, fine aggregate, coarse aggregate, water, and Conplast SP-430 superplasticizer. The analysis of the contour plot concluded that eggshell powder increased the concrete compressive strength at an optimal replacement percentage between 5% and 10%. However, the partial cement replacement with eggshell powder is more optimal for mix design with higher water content. The statistical results of the model, such as R², adjusted R^2, and root-mean-square error (RMSE), indicated that both MR and RSM models are powerful tools to formulate and predict the eggshell concrete compressive strength. However, RSM models showed better accuracy and lower deviation.

This article presents the implementation of a multi-criteria decision support method in the management of multi-source switching systems. We implement the Analytic Hierarchy Process (AHP) in order to solve problems relating to multi-source switching systems. This method reduces undesired multiple switchings bothering the output signal and perceived as electrical perturbations for sensitive charges. The advantage of this approach is that it makes it possible to compare several criteria that are difficultly customisable, using a sole optimisation function. As solution to curb issues relating to the implementation of AHP in real time as descrribed in the literature, we propose an algorithm for aggregating criteria, sub-criteria and alternatives, of which the ultimate goal is to switch to the alternative source offering the best compromise amongst a variety of contradictory. To approve the proposed AHP method, we implement an expert source management system in a Labview environment, which reproduces the same switching conditions in real time.

This paper describes the comprehensive thermal stress analysis and solution of simply supported functionally graded plates. Here, heat conduction formulation has been analytically simplified to access the exact temperature profile and the plate's thickness. Mathematical manipulation within basic elasticity equations has formed a two-point boundary value problem directed along the plate thickness. Here 4th order Runge-Kutta-Gill method has been adopted for numerical integration during the analysis of a group of coupled first-order ordinary differential equations. Thermoelastic constants such as modulus of elasticity, heat conductivity, and thermal expansion were supposed to change exponentially in the direction of the plate's thickness. The ratio of lateral strain to linear strain remained unchanged. Stress analysis has also been carried out by considering the thermal field change along the plate's thickness direction as per simple exponential law. For identifying a variation in structural response, stress analysis results have been compared with stress analysis for the exact thermal field acquired from the equation of heat conduction solution.

This study aims at investigating the effects on asphalt cement (AC) rheology when adding Nano Clay (NC) and Nano Zinc Oxide (NZnO) compounds. The tested contents of NC were 8%, 10%, and 12%, while those of NZnO were 1%, 2%, and 3% by weight of the AC. The study used AC of 60/70 penetration grade since it is the most commonly used in the Middle East region. Different tests were performed on both the control AC (CAC) and modified AC (MAC), including dynamic shear rheometer (DSR), Softening point (SP), penetration, flash and fire points (FFP), bending beam rheometer (BBR), and viscosity tests. These tests' results demonstrated that the modifiers tend to decrease the penetration values but increase the FFP, viscosity, and SP values. A slight improvement in the rheological properties of AC at high temperatures was also evident from the addition of NC or NZnO. Furthermore, adding either modifier led to significant improvements at low-temperature conditions in the AC's performance and cracking resistance. The optimum modifiers of NC and NZnO were 10% and 3% by weight of the AC, respectively.