International Journal of Engineering
Volume:37 Issue: 5, May 2024

Dealing with problematic soils is one of the most challenging parts of geotechnical engineers’ careers. Loose sand is one of them due to its low cohesion and can be found worldwide, specifically in coastal regions. Chemical stabilizers like cement are of the prevalent ones among engineers to deal with the weaknesses of loose sand. However, the substitution of these traditional stabilizers with pozzolanic materials like natural zeolite become approved since it helps reduce cement consumption and hence, lower CO2 emission. Despite all advantages, brittle behavior is an unwelcome consequence of these stabilizers. Therefore, the aim of this study is to reduce the brittleness of the cement-zeolite-stabilized sand employing natural kenaf fibers. To this end, two cement contents, four amounts of zeolite replacement of cement, and three fiber contents in three lengths were adapted in two relative compactions (RC) to investigate the compaction, 8-shape direct tensile strength (DTS), and indirect tensile strength (ITS) behaviors. Experimental efforts revealed that compaction behavior is sensitive to stabilizer contents and fiber content and length. The addition of the 8% cement, increase of the zeolite up to 50%, and fiber increment up to 1.5% led to the reduction of the compaction properties; however, optimum moisture content increased with the rise in kenaf fiber. A notable influence on the DTS and ITS behavior was observed while 30% zeolite replacement in 8%-cemented samples and reinforced with 1% kenaf fiber with 10mm length. Furthermore, a linear relationship was presented between DTS and ITS. In the end, the reinforced sample was analyzed using Scanning Electron Microscope (SEM) images.

5G communication technology supports the Internet of Things, remote health care centers, and cloud computing by tuning their communication services over a very wide range of frequency bands with low-cost, low-battery consumption, and low latency. However, the development of such wireless technology is highly dependent on radio frequency spectra. The Cognitive Radio Sensor Network (CRSN) is an excellent candidate to improve radio spectrum utilization and manage the heavy communication data traffic in 5G wireless networks. CRSN can sense the frequency channels, making it possible for secondary users (who are denied service) to use the free channels. Despite the outstanding features of CRSNs, some limitations overshadow their performance. The most critical limitation is energy and its optimal consumption to increase the network's lifetime. Recent research has shown that energy harvesting can be an effective way to increase the lifetime of CRSNs. However, the sensors should sense the frequency spectrum with a high success rate. In this paper, several optimal sensor nodes using energy harvesting with the approach of increasing the network's lifetime are proposed to solve the mentioned challenge. This way, the sensor nodes are divided into two independent groups for simultaneous spectrum sensing and energy harvesting in each time frame. We will solve this problem based on mathematical optimization and the use of proposed solutions for convex problems. Finally, simulations are developed to evaluate the ability of the proposed solution, assuming the systems use IEEE802.15.4/Zigbee and IEEE802.11af.

This article presents a new lower limb orthosis for helping weak knees during human locomotion. The orthosis structure has 10 degrees of freedom. It utilizes a series elastic actuator, equipped with an elastic rope that transfers torque generated by the motor to the orthosis link. The performance of the proposed lower limb orthosis is virtually simulated by using ADAMS-MATLAB Co-simulation software. The orthosis is designed based on the anthropometric data of a normal human body with a mass of 76 kg and a height of 180 cm. The simulation scenario involves walking with an average speed of 1 m/s on a straight path, and the knee orthosis can bear 40% of the torque exerted by the knee joint during the gait cycle. The simulation aims to evaluate the effectiveness and efficiency of the orthosis in assisting the weak knee joint. The simulation results indicate that The orthosis reduced the knee joint torque by more than 13 Nm in a healthy person, which indicates lower forces on the weak knee. Moreover, the orthosis decreases the maximum energy needed per gait cycle, which implies a higher efficiency and reduces the metabolic cost of the body in the gait cycle.

Polyethylene pipeline is an essential infrastructure of gas distribution network, and there are some problems such as complex damage assessment and tedious assessment process. How to choose an effective damage assessment method for polyethylene pipelines is the focus of the implementation of the gas distribution network at present. In this paper, a nonlinear directional wave method is proposed to detect the damage of polyethylene pipeline by an acoustic wave, and the damage results of polyethylene pipeline are searched. The rationality of this method is verified by calculating the aerodynamic equation.The results show that the nonlinear fixed wave method can accurately determine the damage and crack propagation degree of the pipeline and simplify the damage assessment process, and the results are superior to the linear directional wave method. Therefore, the nonlinear directional wave can be used to assess the damage to ethylene pipelines in gas distribution networks, which has strong rationality and practicality and provides support for the actual pipeline damage assessment.

The utilization of microchannel heat sinks stands as one of the most reliable solutions for dissipating heat generated in electronic chips. In this numerical study, a fractal microchannel heat sink employing three nanofluids Cu-water, Al2O3-water, and TiO2-water with variable volume fractions of 2 and 4 percent as the cooling fluid within the microchannels was investigated. The fluid flow inside the microchannels was analyzed from both hydrodynamic and thermal perspectives. The parameters such as pump power, Nusselt number, and performance evaluation criterion (PEC) were studied. Results demonstrate that heat transfer increases with an increase in the flow rate and volume fraction of nanoparticles. The maximum temperature reduction for the Cu-water nanofluid at an inlet flow rate of 200 ml/min and a volume fraction of 4% is 2.41%, the highest among the investigated nanofluids. However, this nanofluid also exhibits the highest pressure drop, reaching 25% at a 4% volume fraction. The PEC number analysis reveals an overall performance increase for all three microchannels. The Cu-water nanofluid exhibits the best comprehensive performance, providing an 8% overall enhancement, followed by Al2O3-water and TiO2-water nanofluids, which increase the system performance by 5% and 4%, respectively. Furthermore, the study introduced fins and cavities to the microchannel branches to enhance heat transfer and overall performance. Results indicate an increase in heat transfer for both modified geometries. The microchannel with fins exhibits a 3.5% lower maximum temperature compared to the original geometry at an inlet flow rate of 200 ml/min, while the microchannel with cavities showed a 1% reduction. However, the microchannel with fins experiences a 400% higher pressure drop than the initial geometry, while the microchannel with cavities has a 4% increase. PEC number analysis demonstrated that the microchannel with cavities improves system performance by 8%, whereas the microchannel with fins reduced system performance by 4%.

With the growing movement of using direct current (DC) load demands, as well as DC distribution generations (DGs), the distribution system has undergone significant changes on the production and demand side. Due to alternating current (AC) and DC generators and load demands, it is not cost-effective to continue in the AC distribution system. Therefore, AC/DC hybrid distribution system planning is economical despite various demands and generations. On the other hand, uncertainty in load demand and output power of DGs cause the possible behavior of the distribution system. This behavior leads to risk in the distribution system. In this paper, the AC/DC distribution system planning is discussed by considering the risk. The planning problem in the matrix laboratory and general algebraic modeling system (MATLAB/GAMS) hybrid space has been formulated and solved. Using the K-means algorithm, the uncertainty related to renewable DG output power and load demand has been modeled. To verify the proposed method, it was implemented in a sample distribution system.

This paper investigates the electrical behavior and performance of a  Dual Metal Gate Overlap on  Drain Side Tunnel Field Effect Transistor with Spacer (DMG-ODS-TFET) in 10 nanometer technology. In this design, the utilization of two different metals to create the gate effectively maintains electrostatics and minimizes gate leakage current. This structure is formed by silicon dioxide and hafnium oxide as dielectric materials. The drain current characteristics such as subthreshold swing, on-state current, off-state leakage current, and transconductance are calculated for the proposed device using the available two-dimensional numerical device simulator silvaco tool. The characteristics of the proposed device vary with changes in channel length, doping concentrations of the drain and source, and the thickness of the oxide layer. This structure shows a lower off current, and better on-to-off current ratio with improved drain current. Consequently, the proposed design effectively balances gate control and leakage current, resulting in superior to conventional and dual metal gate devices. Based on improved performance parameters, this proposed structure is suitable for high-frequency applications.

This paper presents an investigation on changes in viscosity and group composition of heavy oil samples after ultrasonic upgrading process. Heavy oil samples correspond to different oilfields (located in Russia) were processed under various ultrasonic mode, the cavitation consequence of which was controlled by acoustic method. The viscosity of samples was measured just after ultrasonic treatment, 10 minutes, and 1-34 days. The saturate, aromatic, resin and asphaltene (SARA) analysis was carried out after ultrasonic treatment with 34 days of relaxation and the achieved results were compared with the SARA fractions of original crude oil. The results of viscosity measurement showed viscosity reduction after the ultrasonic treatment. However, the viscosity was regressed after 1-4 days of relaxation with further reduction in 7 days. The degree of viscosity increase after 34 days was only 10% in contrast to viscosity of original crude oil. The power and the sonication time did not influence the relaxation process. In conclusion, attention was drawn to the results of SARA analysis, the content of saturates decreased and the relative content of heavy fragments such as resins and asphaltenes was increased, which determines the degree of viscosity increase after relaxation period.

Oil-water emulsion causes a wide range of problems, one of which is the emergence of significant decreases in pressure in flow lines resulting in higher pumping and transportation costs. The most widely developed trend among oil/water separation technologies is using demulsifiers based on magnetic nanoparticles (MNPs). MNPs have specific chemical and mechanical properties, providing unique opportunities to solve oil production issues. The key features of such magnetic nanoparticles for their sustainable application are their reusability and stability; the opportunity of remote manipulation using external magnetic fields gives them a singular benefit in transport operations. The main objective of the study is the systematization of MNPs researches for effective oil and water emulsion separation. This review provides MNP demulsifier characteristics, Oil-water emulsions (OWE) separation mechanism, and factors influencing oil-water emulsions efficiency disruption by MNP demulsifier. The relevance of this study is that oil-water emulsions are often encountered in practice during field development. To solve this problem, the use of demulsifiers based on magnetic nanoparticles is proposed. The novelty of the work lies in the fact that the work collects several factors affecting demulsification at once and describes the impact of each factor. Among these factors, the most influential are: emulsion characteristics, water salinity, pH, reservoir temperature, addition of chemical surfactants, time and magnetic field. The mechanism of formation of oil-water emulsions of various types is also described, and negative consequences of emulsion formation are discussed. The results showed that the magnetic nanoparticles need a protective layer and the demulsifier should have good wettability by the continuous phase of the emulsion.

The cooling rate under impingement of air jet finds massive application in electronic packaging, material processing industries and cooling of gas turbine. The conventional cooling of heat sinks was till date carried out using a fan and pump. Recently, the momentous impingement of air has been found to produced 1.5 times the cooling rate, as compared with conventional method, under same pumping power. Previously, attractive amount of Research is carried out in observing the cooling rate for constant heat flux boundary condition, and less are available for constant wall temperature. The present research provides an in-depth numerical investigation for such jet impinged heat sinks, with a heat flux boundary condition. The exponential variation of heat flux magnitude with radial distance (Away from impingement point), is observed to be a generic alternate of constant wall temperature boundary condition. The numerical computation for heat transfer of such exponentially powered heat flux sink is carried out using FLUENT (ANSYS 2023R1). An orthogonal 2-D mesh computational domain with a compactible SST and K-Omega turbulence model is simulated for various inlet velocity and nozzle-target spacing. The impingement of jet and local cooling of target surface is defined using a well know non-dimensional Reynolds and Nusselt number, respectively. The exponential power for non-uniformly heated sinks can be readily selected (0.1-1) to replicate the present non-uniform heating or constant wall temperature boundary condition. Non-uniform heating has gained lots of attention of heat transfer researcher across the globe. The computation results extracted for various impinging Reynolds number and nozzle-target spacing, were closely best fitted using regression and validated with referred previous literature results. Tight dependency of slope parameter, over Reynolds number and z/d is observed in local cooling rate.  These dependencies are judged based on the power of exponents. The semi – empirical correlations are defined separately for and stagnation, transition, and wall jet regions, separately. Such correlation can plan the design of cooling system, under non-uniform heating conditions

This study aims to investigate the use of refractory brick (RBA) by-products as a substitute for coarse aggregate in sustainable concrete production. Concrete mixes with water-to-binder (w/c) ratios of 0.52 and 0.49 and containing 0%, 15%, 30%, and 50% RBA as a partial replacement for ordinary crushed stone (OCS) were produced. The following properties were examined in this study: workability, compressive strength, stress-time relationship, toughness index, performance criteria, and cost analysis. The test results showed that an increase in the RBA percentage in the concrete mixtures positively contributed to concrete workability. Moreover, the compressive strength and all phases in the compressive stress and time relationship decreased as the percentage of RBA in the concrete mixture increased. However, at 15%RBA, the toughness index value was comparable to that of the reference concrete, whereas based on the performance criteria, the replacement of OCS with 15%RBA for both water-cement ratios met the minimum requirements. Meanwhile, cost comparison analysis discloses that material and production costs can be reduced by approximately 51.84% and 1.5–6.5%, respectively. Based on the analysis of all the test results, 15%RBA exhibited insignificant differences in value compared with the reference concrete. Thus, the use of 15%RBA as an OCS replacement is an acceptable and viable option for producing sustainable concrete.

In today's dynamic and unpredictable world, the planning and management of humanitarian supply chains hold paramount importance. Efficient logistics management is crucial for effectively delivering essential aid and resources to affected areas during disasters and emergencies, ensuring timely support and relief to vulnerable populations. In this research, we addressed a novel humanitarian supply chain network design problem that considers product differentiation and demand uncertainty. Specifically, we simultaneously incorporate non-perishable, perishable, and blood products as critical components of the network. The problem is formulated as a multi-objective mixed-integer linear programming model aiming to minimize the total cost and total traveled distance of products by making location, allocation, and production decisions. To enhance realism, we account for demand uncertainty in affected areas. To tackle this challenging problem, we proposed a two-phase solution methodology. Firstly, we employed a robust optimization approach to establish a deterministic counterpart for the stochastic model. Subsequently, an efficient fuzzy programming-based approach reformulates the model into a single-objective form, effectively accommodating decision-makers' preferences. Numerical instances are solved to investigate the performance of the model and solution methodologies. The results demonstrate the effectiveness of our fuzzy approach in finding non-dominated solutions, enabling decision-makers to explore trade-offs. Also, sensitivity analyses were conducted to provide more insights. Finally, some suggestions are presented to extend the current work by feature researchers.

This research has been carried out with the aim of evaluating the energy, economic and environmental performance of selected countries that export energy resources with the integrated approach of data envelopment analysis (DEA) and game theory. The methodology of this research, including super-efficiency and cross-efficiency methods have also been used to rank efficient countries before the cooperation phase. Then, in the cooperation phase, each country is investigated using the method of cooperative games theory and Shapley's value. The resulting model was implemented and the rank of the efficient countries was compared with each other in the super-efficiency and cross-efficiency method (before cooperation) and the Shapley’s value method (after cooperation). The results showed that Qatar and Yemen have the highest, Lebanon and Jordan the lowest energy efficiency; Kuwait, Qatar and Turkmenistan have the highest economic efficiency, Iran and Turkey have the lowest economic efficiency; UAE and Qatar have the highest, Iran and Jordan the lowest environmental efficiency.