Arabian Journal for Science and Engineering最新文献

This sentence discusses a possible solution to overcome the disadvantages of traditional eccentrically braced frame systems (EBFs). The proposed solution involves separating the shear links from the frame beams and utilizing double-tube buckling restrained braces with contact rings. These modifications aim to improve the overall performance of the frame system. To investigate the mechanical characteristics of this structural system, an experimental study was conducted, involving the design of two K-type EBFs and testing four distinct replaceable shear links. The stress distribution, load–displacement curves, and hysteresis curves of this structural system were obtained by conducting cyclic lateral loading tests on these specimens. Subsequently, the hysteretic properties, load bearing capacity, and deformation capacity of the member underwent analysis. An exploration was conducted into the primary influences on the structural mechanical characteristics. The research indicates that the double-tube buckling restrained braces with contact ring enhance the structural strength and synergistically perform with shear links to dissipate energy, while ensuring improved performance. Comparison of the date of different parameters shear links shows that the placement of stiffening rib increased the energy dissipation performance by 41.2% and shear capacity by 14.6% for the same sectional dimension of shear links. In the shear links with two stiffening ribs, the larger sectional dimension improved the energy dissipation performance by 11.3% relative to the shear links with smaller sectional dimension. For the shear links with one stiffening rib, the increase in sectional dimension, on the contrary, reduced the energy dissipation performance by 18.4%

Aluminum parts are used in the aviation industry because of the need for light. However, in addition to lightness, critical parts that must have high strength properties have also been developed. The corrosion resistance, resistance to high temperatures, and workability were investigated in this case. It becomes difficult to choose among many aluminum materials that can be alternatives to each other when these features are included. The developed approach, which considers many of the features listed above and ultimately recommends to the user the most suitable aluminum material for the relevant critical part, will be used in overcoming the difficulties in this process. A material selection model is proposed in this paper for this purpose, and the decision-making model is demonstrated with examples from the aviation industry. Therefore, the developed model, which will enable the selection of the most suitable materials among alternative materials, especially for critical parts in the aviation industry, will guide professionals working in this field. For this purpose, the fuzzy TOPSIS method is used in the study, and suitable alternatives are determined. Finally, a robustness analysis is proposed to determine the most suitable aluminum material for highly uncertain situations. We apply a stability evaluation study based on process control theory in the robustness analysis.

In this study, the solubility of Triamterene (TRM), a diuretic drug, in pure and ethanol-modified subcritical water (SCW) was investigated by a static method. Experiments were performed at high temperatures (363.15–433.15 K) with co-solvent (0–10% w/w ethanol) at a pressure of 20 bar. Increasing the temperature and weight percentage of ethanol significantly increased the mole fraction solubility of TRM. The mole fraction solubility of TRM in pure water (0% wt ethanol), 5%wt ethanol, and 10%wt ethanol was obtained in the range of 0.73 × 10^–4–1.56 × 10^–4, 0.73 × 10^–4–1.82 × 10^–4, and 0.78 × 10^–4–2.16 × 10^–4, respectively. For the correlation of experimental solubility data, linear and modified Apelblat models were selected. The values of ARD and RMSD were calculated as indicators of the accuracy and validity of the models. The modified Apelblat model showed the best performance in correlating the experimental solubility data. Finally, the dissolution thermodynamic functions (({Delta }_{dis}{G}^{^circ }), ({Delta }_{dis}{H}^{^circ }) and ({Delta }_{dis}{S}^{^circ })) were calculated for the solubility of TRM in pure and ethanol-modified SCW.

Sediment transport is essential for the estimation of the life of dam reservoirs. Arid regions lack sediment transport studies due to the lack of measurements for either water or sediment, and therefore, the life of dam reservoirs cannot be estimated accurately. We developed a power law sediment rating curves from measurements from 7 gaging stations of some subbasins in southwestern Saudi Arabia. These curves are developed for each subbasin and a generalized equation of the two basins are also developed. The regression parameter “a” ranges from 0.0008 to 0.0088, and the power “b” ranges from 1.3753 to 1.7223. Validation and cross-validation were performed on two Wadis namely: Wadi Yiba and Liyyah basins. The developed equations were used to estimate the sediment yield of the study area. The results show that the regression parameters of the sediment rating curves vary from one subbasin to the other and that the sediment per unit area ranges from 88 to 374 Ton/km²/year for Wadi Yiba, and from 297 to 1324 Ton/km²/year for Wadi Liyyah. The cross-validation of the equations developed for the two Wadis showed R² = 0.99. The t test supported the null hypothesis of having no significant difference and therefore indicated the possibility of applying Yiba/Liyyah rating curve to other regions in Saudi Arabia. Hydrologists and/or engineers are advised to utilize the developed equations to estimate the lifespan of a dam reservoir, by acquiring the dam design data, gathering current rainfall data, conducting rainfall-runoff modeling to account for the old data, and then applying the derived equation.

Geopolymer lightweight cellular concrete (GLCC) combines the advantages of geopolymer and LCC but also suffers from the inherent deficiency of low strength, which can be improved by introducing suitable reinforcing materials such as fibers. This paper investigated the mechanical properties and microstructure of fly ash-slag-based GLCC reinforced with glass fibers (GLCCRGF), aiming to reveal the strengthening mechanism of glass fibers. The effects of different fiber contents (0.0, 0.3, 0.6, 0.9, and 1.2%), fiber lengths (3, 6, 9, 12, and 15 mm), and fiber-blending methods (G-R, G-W, and G-S) on the mechanical properties of GLCCRGF were analyzed. The results showed that the fiber incorporation had no significant or even negative effect on the compressive strength but significantly improved the splitting tensile strength. The optimal results of fiber content, fiber length, and fiber-blending method are 0.6%, 9 mm, and G-R, respectively. From the microstructure perspective, optical tests were conducted to explore the evolution rules of pore size, pore shape factor, and fractal dimension of pore distribution of GLCCRGF. The results showed that the incorporation of glass fibers (0.6%, 9 mm, and G-R) improved the pore characteristics and contributed to more uniform pore distribution. Furthermore, scanning electron microscopy (SEM) was employed to observe the micromorphology of the skeleton structure of GLCCRGF. The SEM results showed excellent interfacial bonding between glass fibers and the geopolymer matrix. Due to good bonding quality and crack-bridging effect, the presence of glass fibers enhanced the strength and crack resistance of the matrix.

Water resources in arid and semi-arid regions are constrained by several critical problems, including scarcity of water resources and extensive use of groundwater. Climate change and population growth will certainly result in a decline in water tables and degradation of groundwater quality. The purpose of this study is to create rainwater retention ponds in the Najran Valley located at the southern border of Saudi Arabia. Over the past decade, various researchers have reported a sharp decrease in the availability of water in the area. In addition to urban sprawl, excessive groundwater extraction is the primary cause of the decrease. Even though the valley receives a sufficient amount of rainfall throughout the year, there is no adequate rainwater management system in place. As a result of this combined water management issue, the authorities are seeking additional water storage options in addition to the Najran dam reservoir. To evaluate the flood characteristics of the region, an extensive GIS-based hydrological study is conducted. To estimate flood volumes, the critical flood-prone areas are identified and their catchments are calculated. To store rainwater generated by these catchments during rainfall events, a variety of suitable locations have been proposed for retention ponds. The construction of retention ponds would have numerous environmental benefits in addition to solving the problem of water scarcity. As a result of the study, the authorities will be able to implement a management strategy that maximizes the use of the region's water resources.

This study introduces a novel control approach for a twin rotor multi-input multi-output system (TRMS), specifically targeting the pitch and yaw movements. The proposed method employs a sliding mode controller (SMC) with variable gains, aiming to overcome limitations like chattering and excessive control effort. Unlike traditional controllers, the gains here dynamically adjust based on the error state, enhancing the robustness of the system against external disturbances and parameter uncertainties. The control algorithm draws inspiration from both first-order and higher-order sliding mode controllers. To rigorously assess the robustness of the controller, Gaussian White noise is incorporated into the model. By dynamically adjusting gains, the proposed approach aims to minimize control effort while mitigating control signal overestimation arising from model uncertainties. Furthermore, stability analysis confirms that the operating point of the closed-loop system converges within a finite time. The effectiveness of this novel controller is validated through simulations using the MATLAB/Simulink environment.

The flux observer method is widely utilized as a sensorless control technique in which the stator or rotor flux of IPMSM can be measured with a closed-loop observer or an integrator. However, DC-offset (DCoff), the ramp signal, and harmonics are consistently present in the acquired rotor flux because of an unidentified starting value, errors in the integral computation's current detection, and the inverter's nonlinearity. The aforementioned interference signals will drastically reduce the sensorless control efficacy. This work introduces an enhanced flux estimator with a negative feedback loop and PI controller to overcome the DC drift problem resulting from a pure integrator and a low-pass filter. Moreover, an optimal design approach of flux estimator structures with a broad range of speeds for Interior permanent magnet synchronous motor (IPMSM) drives is proposed, which utilizes an integrated topology of the voltage and current models incorporating a DC-offset PI-correction loop, actual and estimated flux magnitude's correction error. The flux vector's initial inaccuracy is eliminated, together with the DCoff and drift in the acquisition channel. A phase-locked-loop state estimator is utilized to derive the speed and position from the actual and estimated flux. The effectiveness and superiority of the suggested approach were proven by simulation and experimental findings for the IPMSM drives, which displayed high dynamic performances over varying scenarios. This reliable approach, including sensorless control, is suitable for all AC motors with sinusoidal flux distributions over a wide speed range.

This study aimed to investigate the effects of acid corrosion on mechanical properties and fractal characteristics of red sandstone. The mineral composition of red sandstone was analyzed using X-ray diffraction. The mechanical properties and acoustic emission (AE) signals of red sandstone specimens corroded by sulfuric acid solution with pH values of 1, 3, and 5 for 30 days were determined by uniaxial compression test and AE technique. The energy dissipation law and the fractal damage characteristics of red sandstone specimens after acid corrosion were analyzed based on the energy and fractal theories. The results indicated that the compressive strength and elastic modulus of red sandstone specimens corroded by acid solution decreased. In addition, the peak strain increased, the cumulative AE ringing count decreased, and the duration of high-level AE ringing shortened. These phenomena became more pronounced as the acidity of the solution increased. The peak values of the total energy and the elastic strain energy of the acid-solution-corroded red sandstone specimens decreased. The energy absorption capacity and energy storage limit of rock specimens also decreased. The fractal dimension and the degree of fragmentation decreased with the dissipated energy used for fragmentation. This research provides valuable insights into the prevention and control of sub-surface geotechnical hazards in acid rain-prone areas.

Beam-column (B-C) joints are recognized as critical regions in reinforced concrete (RC) moment-resisting frames when subjected to seismic loads. Furthermore, these joints may be subjected to high temperatures during their lifespan, which might cause severe structural damage. Accordingly, the seismic response of RC beam-column joints that were subjected to heat (i.e., 400 °C and 600 °C) was investigated in the present experimental work. The joint specimens were divided into three categories: Three joints were kept as is (i.e., reference joints; no strengthening is applied), whereas six joints were strengthened with one and two layers of stainless-steel expanded metal sheet mesh (SSEMSM) in order to improve their performance. To investigate the seismic performance of the joints, a quasi-static cyclic load was applied to the joints to simulate a seismic load. Results showed that the average maximum load for joints strengthened with one and two layers of SSEMSM, respectively, was increased by 11% and 21% at ambient temperature and by 2% and 9% at 400 °C, in comparison with the reference joint. In addition, using one and two layers of SSEMSM, respectively, led to achieving an average of 91% and 100% of the full capacity of the reference joint for B-C joints subjected to 600 °C. Furthermore, the experimental findings show a considerable improvement in the cyclic response of non-ductile RC joints that were strengthened with the SSEMSM strategy and subjected to high temperatures (i.e., higher load capacity, greater displacement, higher dissipated energy, higher ductility, and slower degradation in the secant stiffness).