International Journal of Engineering
Volume:38 Issue: 3, Mar 2025

This paper presents a novel class of power-dependent bandstop filters (PDBSF) that can be used to effectively suppress dynamic RF interference in scenarios involving 1-variable frequency, 2-variable power, and 3-variable frequency and power. The proposed circuit consists of a signal tracking bandstop filter, an input coupler for measuring the input power, and an electronic feedback circuitry. The PDBSF is implemented using microstrip transmission line technology and simulated using Momentum ADS. The tuning range of the proposed BSF filter is approximately 245 MHz to 295 MHz, while the power range that can be covered is up to 5 dBm. Simulation results demonstrate that the PDBSF can effectively suppress any in-band interference with variable frequency and power.

Regeneration of electric energy during braking is an important issue in electric railway systems. Especially in older electric railway systems that have non-reversible DC traction substations, the goal is to modify the structure of the DC traction substations and replace them with reversible converters at the lowest cost. Accurate evaluation of the power flow and the energy distribution in an electric railway system needs a comprehensive study of the whole railway system with multiple moving trains. But, the modeling and simulation of an electric railway network are complicated due to its nonlinear, time-variant, and large-scale structure. This paper presents the electric energy distribution in the Isfahan Metro Line 1 with and without regenerative braking. For this purpose, a simulator is developed for the DC electric railway systems with multiple moving trains. Driving control strategies, including coasting control, have been applied. The understudy system consists of 7 DC traction substations and 10 trains traveling on the up track. Different scenarios have been simulated with various combinations of reversible and non-reversible DC traction substations. Results reveal that the electric energy consumption of the system with regenerating trains and reversible DC traction substations is 27.13% lower than the system without regenerative braking. To mitigate the energy consumption in the Isfahan Metro Line 1 using the regenerative braking system, it is not mandatory to upgrade the structure of all 7 DC traction substations. Results show that it is possible to reduce electric energy consumption by 26% through installing only 5 reversible traction substations.

This research aims to study the effect of different tool pin shapes on the mechanical properties of friction stir processed (FSP) surface composites. The focus is on fabricating 6061-T6 Al/SiC composites using cylindrical, triangular, tapered cylinder, square, and hexagonal tool pin geometries. The experiments were conducted on a vertical milling machine with H13 tool steel at a transverse speed of 20 mm/min and a rotational speed of 1000 rpm, with three passes. Dye penetrant tests confirmed the absence of surface defects. Microhardness testing using the Vickers method showed that the square pin geometry achieved the maximum hardness value (120 HV). Surface topography analysis using optical and scanning electron microscopy revealed significant grain refinement and fragmentation of silicon carbide particles. Wear tests using a pin-on-disk tribometer indicated that 6061-T6 aluminum alloy without reinforcement exhibited the highest wear rate, while the square tool pin geometry resulted in the least wear rate due to increased microhardness. The processed Al/SiC composites demonstrated a lower average friction coefficient compared to the base metal.

By developing an analytical approach, this study investigates bending and stress analysis of doubly curved laminated composite shells under arbitrary, non-uniformly distributed loads. Using Hamilton's principle and based on the first-order shear deformation theory, the governing equations are derived as five coupled second-order partial differential equations. For the first time, an analytical approach based on the dual power-series solution is developed to analyze doubly curved shells. In this regard, the obtained set of governing equations is solved using the proposed analytical method. Doubly curved laminated composite shells with arbitrary boundary conditions and various distributed loads can be analyzed using the proposed solution procedure. The results obtained in this study were compared with those obtained by the other researchers using the layerwise and higher-order theories. The comparisons showed that the obtained results are in good agreement with the results of other researchers, so the proposed analytical method can be used to analyze doubly curved shells in various loading and boundary conditions. The developed solution procedure uses the three-dimensional theory of elasticity to determine transverse shear stresses. Boundary conditions at the top and bottom of the laminated shell and continuity conditions at the interfaces between layers are exactly satisfied.

The purpose of this study is to demonstrate how variations in soil suction impact shear strength, swelling pressure, and volume changes. To that end, small-scale tests were conducted on both pure bentonite and bentonite in mixtures of 30%, 40%, and 50% with sand under dry conditions, using values selected from compaction curves. A model with dimensions of 700 x 700 x 650 mm for the same starting dry unit weight and water content was utilized to demonstrate the impact of the initial load and history load by loading a surface footing to the permitted bearing capacity. A tensiometer was used to measure the soil suction at 20 and 50 cm depths from the surface footing.  The study found that for all soil types, the values of swelling pressure and potential are affected by the initial load. The initial load decreases pressure and swelling potential for pure bentonite by approximately 29% and 30%, respectively, at optimal drying conditions. Conversely, when the void ratio stays the same, overconsolidated soil expands more than typically consolidated soil by about 19% and 46% for the swelling potential and swelling pressure, respectively, for a pure bentonite soil sample at optimal drying conditions.

The thermoelectric energy between the material and the cutting electrode is essential to the EDM process. This research assesses the new Nano electrodes and input settings for SS205 electric discharge machining (EDM). In order to remove the product electro thermally, parameters such as current, pulse on, and pulse off are taken into account during sequential, independent discharges between the EDM tool and the specimen while using EDM oil as a dielectric fluid. Together with the SS205 electrode work piece, the electrode, which is made of 90% aluminium reinforced with 5% copper and 5% zirconium di-boride, is used for testing. The P/M process is used to create it. To optimize, we use the full-factorial central composite design based on response surface methodology (RSM) to create the set of experiments (20 runs). Analysis of variance (ANOVA) then confirms the suitability of the suggested models. ANOVA determines which process factors significantly influence performance attributes. Die-sinker EDM using an Al-Cu-ZrB2 composite electrode shows promise for lowering production expenses and wear. SEM is used to analyze surface imperfections both before and after machining. Parameters such as Ton of 50μs, T off of 80μs, and SV of 12 amps provide a wear rate of 0.0008 g/min, which is minimal. At 0.0107 g/min, high removal rates are achieved with Ton of 70μs, T off of 90μs, and a SV of 12 amps. The settings for better surface roughness are being optimized further, with the best SR obtained at 2.91μm. Lastly, in order to assess the effectiveness of the chosen desirability technique, the optimized outcomes are verified against the experimental findings.

Ensuring robust security systems is critical, particularly for smallholder palm oil supply chains. This study aims to enhance the security and efficiency of blockchain-based supply chains for smallholder palm oil by exploring the integration of certificate authorities, multi-channel schemes, and smart contract integration. This article focuses on the implementation of security systems in blockchain-based supply chains for smallholder palm oil using Certificate Authority (CA), Multi-Channel Scheme (MCS), and Smart Contract Integration (SCI). The methods used included problem identification, data collection and analysis, privacy and security model development, prototype development, system privacy and security evaluation, and system performance measurement. The results show that implementing these security systems can significantly improve security, efficiency, data integrity, authentication, and trust in palm oil supply chains. Performance measurement is used to evaluate transactions and the implementation of security mechanisms implemented in the system by measuring throughput, send rate, latency, and resource utility. Our research addresses security, efficiency, and performance in blockchain-based smallholder palm oil supply chains by introducing certificate authorities, a multi-channel scheme for data segregation, and a novel smart contract framework, and evaluating their combined impact on system performance metrics. The research provided insights into ongoing efforts to secure and optimize smallholder palm oil supply chains and offered insights into these technologies' practical applications and benefits. These findings provided valuable recommendations for the adoption and integration of these technologies in the palm oil industry to improve supply chain security, transparency, trust, traceability, and efficiency.

The salient advantages of inverters based on impedance source networks have made them proper for renewable energy conversion applications that are required to increase input DC voltage and convert it to AC energy. Switched Boost Inverters (SBI) are single-stage DC-AC power converters utilizing an active switch in the impedance network whose output voltage can be greater or less than its input DC voltage. This paper introduces a modified quasi-Z-source inverter (qZSI) structure with an active or quasi-switched boost inverter (qSBI). The suggested inverter provides a high boost factor with a small shoot-through interval and a high modulation index. The distinguished features of the suggested inverter are continuous input current and low voltage stress of switches. Moreover, despite the significant impedance source inverters, the suggested inverter is deprived of initial inrush current. Hence, the input voltage ripple is slight. Operation principles and requisite analyses have been represented, and comparisons based on various parameters with similar inverters have been carried out to showcase the superiority of the suggested inverter. Simulation results have been carried out in MATLAB\Simulink environment. The experimental results validate the accuracy and performance of the suggested inverter.

Deteriorated segmental beam failure in civil engineering constructions is caused by environmental conditions, material deterioration, and design errors. Effective maintenance and rehabilitation techniques require a thorough understanding of these reasons. Chloride-induced corrosion of reinforcing steel due to marine circumference cycles causes corrosion, bond losses, and reduced beam capacity. Structural distress can result from reduced steel cross-sectional area or loss of bond between concrete and reinforcing steel. The current research focuses on studying the effect of deterioration (accelerated corrosion process) on the structural performance of prestressed precast concrete segmental beams under concentric and eccentric loads. Six segmental beam specimens with 1800 mm length and hollow cross-section dimensions of 300×300 mm were tested. The adopted variables included the presence or absence of damage (corrode), load type (concentric or eccentric), and presence or absence of externally bonded carbon fiber reinforced polymer strips. All beam specimens were clamped at the ends, then the middle segments were loaded by applying a vertical load with eccentricities of 0, and 100 mm to achieve the required bending and torsion. It was concluded that a 15% corrosion of reinforcement causes a deterioration of concrete strength, which leads to a decrease in the ultimate load-carrying capacity by about 23% under concentric load and 19% under eccentric load. It found that as vertical deflection and twist angle increased, in accompanied with the vertical load, the deteriorated specimens experienced a gradual degradation in the stiffness. When compared to control specimens, repaired specimens demonstrated superior load-carrying and energy-absorbing capabilities.

This study introduces a new approach to Pulse Width Modulation (PWM) known as the adapted DC level shift PWM technique (DC-PWM), which is applied to a nine level modular multilevel converter. This modulation technique involves interleaving the modulated waveform with a Direct Current (DC) level, while ensuring that quarter wave symmetry is preserved. By implementing an adjusted level shift 1/4 DC-phase disposition (PD) PWM and 2/4 DC PDPWM modulation technique, the switching frequency of the Nine level Modular Multilevel Converter (MMC) has been successfully reduced. The technique's effectiveness has been confirmed through validation using Simulink/MATLAB and an experimental setup. The simulation results show a notable decrease in the frequency of action switching. When it comes to harmonic performance for phase voltage, line voltage, and capacitor voltage, the Type-3 1/4 DC-PDPWM technique generally outperforms the 2/4 DC-PDPWM technique. The 2/4 DC-PDPWM Type-2 demonstrates impressive performance, particularly in terms of phase current and capacitor voltage %THD. The selection of these techniques will be determined by the specific performance needs and the trade-offs in complexity and harmonic suppression that are deemed acceptable for the intended use.

This research aims to investigate and develop the wear properties of the copper-graphene composite, which is utilized in electrical contacts, the railway, and electronics industries. In this research effects of annealing temperature on wear resistance and microstructure in copper-graphene composite fabricated by the accumulative roll bonding (ARB) method was studied. The samples were annealed at 200 (S200), 300 (S300), and 500 °C (S500) for 1.5 hours. The wear test was performed using a steel (Chromium steel) pin and the pin-on-disk method with a normal force of 10 N. In addition, wear tracks were analyzed using scanning electron microscopy and energy-dispersive spectroscopy. An adhesive wear mechanism was observed in all samples. With the increase of annealing temperature, the mechanism of oxidation and adhesive wear changed to scratch, groove, and dullness along with severe plastic deformation. Regarding the wear properties, the results showed that the wear rate increases with the increase in the annealing temperature. This way, the wear rate reached from 1.16 × 10-6 g/m in the R sample to 3.15 × 10-6, 3.93 × 10-6, and 6.34 × 10-6 g/m in the S200, S300, and S500 samples. By examining the microstructure of the annealed samples and comparing them with R (as-fabricated sample), It was observed that with increasing annealing temperature, the grain size in S200, S300, and S500 samples increased from 6.63 to 9.67, 14.3 and 16.79 µm, respectively. The microhardness of the S500 sample decreased by 45.11% (From 121.12 to 58.47 Hv) compared to R, which was ascribed to grain growth.

This study used convolutional neural networks (CNN) to manage the quality of resistance spot welding by categorizing photos of welds on galvanized steel sheets. The welding parameters included 19 cycles of welding time, 8.5 kA welding current, and 0.20 MPa electrode force. Endurance testing procedures were used to generate a dataset for the CNN model. Following that, weld surface photos were collected, nugget sizes were determined, shear strength was tested, the influence of zinc coating on the workpiece was investigated with a scanning electron microscope, and data was analyzed to classify the quality of the weld surface using K-fold cross-validation. The model was created with the pre-trained ResNet50 architecture and fine-tuning procedures. According to the research findings, the CNN model achieved the greatest accuracy of 93.93%, with precision, recall, and F1-Score values of 0.996, 0.998, and 0.997, respectively. The effect of the zinc coating was detected during the 270th welding cycle, revealing deformation of the electrode contact surface and melting of the zinc coating, which, when paired with the copper electrode, resulted in the creation of brass deposits on the electrode contact surface. This impact caused the nugget size to fall outside of permitted limits, reducing shear strength.

With the intensification of global climate change and environmental degradation, achieving urban carbon peak and carbon neutrality has become a common focus of international attention. Traditional optimization methods often overlook uncertainty factors and dynamic changes in data when dealing with urban energy systems and carbon emissions issues. Therefore, this study introduces random matrix theory and proposes a new path and method for urban carbon peaking and carbon neutrality. This work explores the concept of building thermal inertia in depth and establishes a mathematical model of building temperature considering thermal inertia, providing strong model support and theoretical basis for the formulation of optimization strategies for community level integrated energy systems. By analyzing the total and per capita carbon emissions at the provincial level, the distribution pattern of "high in the north and low in the south" was revealed, and the important impact of climate factors on carbon emission differences was emphasized. Through a double-layer optimization algorithm, we fully utilized the thermal inertia of buildings and achieve more economical carbon emission optimization than traditional algorithms. In addition, we also used the relative index of the Theil index and the absolute index of the Gini coefficient to rigorously test the fairness of the allocation results, and the results showed that the per capita carbon emissions of Chinese urban residents in 2025 after comprehensive allocation were relatively fair. This study not only provides new theoretical support and empirical methods for urban carbon peaking and carbon neutrality, but also helps to promote fair distribution of carbon emissions at the provincial level, providing useful references for achieving national and even global low-carbon development goals.

The purpose of this study is to investigate the effect of high temperatures on the mechanical properties of lightweight geopolymer concrete made of palm oil industrial waste materials known as palm oil fuel ash (POFA) and oil palm shell (OPS) as binder and coarse aggregate in geopolymer concrete would give an added advantage in both environmental and economic aspects with alkaline activator to binder (AK/B) ratios of 0.3 and 0.6. For each (AK/B) ratio, POFA was replaced with 0%, 10%, 25%, 50%, and 100% of fly ash (FA). To that purpose, the mechanical properties of OPS geopolymer concrete (OPSGC) produced using POFA, FA, and OPS are examined in terms of compressive strength, splitting tensile, and flexural strength. To determine the compressive strength loss for each mixture, the geopolymer concrete samples were subjected to high temperatures of 200°C, 400°C, 600°C, and 800°C. The test findings showed that increasing the alkaline activator to binder (AK/B) ratio at 3, 7, and 28 days increased the compressive strength. Generally speaking, exposure to temperatures above 200°C causes the OPSGC to increase in compressive strength. Following exposure to temperatures as high as 400 °C, the OPSGC's strength began to decline. AK/B ratio of 60 are less affected by high temperatures than mixes made with an AK/B ratio of 30. The miture of 25% POFA content, AK/B ratio of 0.6, and oven curing provided the maximum strength of 30.9 MPa and Less strength loss compared to other options.

Dredged sediments from dredging operations pose environmental hazards and disposal challenges. The geopolymerization method for treating these sediments offers an eco-friendly alternative to Portland cement. This study develops geopolymer materials using uncalcined dredged sediment, fly ash, and an alkali activator (sodium hydroxide and sodium silicate). The compressive strength of the geopolymer was tested after 7 days curing under two conditions (ambient and at 60°C for the first 24 hours) and analyzed using Box-Behnken Design and Response Surface Method. The study examined three variables: sodium hydroxide molarity (6M to 12M), sediment-to-total solids ratio (0.3 to 0.9), and sodium silicate solution-to-sodium hydroxide solution ratio (1 to 3). High-accuracy prediction models were established, and the desirability function was used to optimize the mixture proportions for the two curing conditions. The multi-objective optimization aimed to meet the strength requirement of TCVN 6477:2016 standards for concrete bricks, maximize dredged sediment content, and minimize sodium silicate usage. The optimal mixture achieved a compressive strength of 7.5 MPa at 7 days, with 37.53% dredged sediment for ambient curing and 45.59% for drying curing. Compared to ambient curing, drying curing enables a higher sediment content and a reduced use of NaOH. Furthermore, the geopolymer reactions and gel matrix formation of the optimal mixture were confirmed by FTIR spectra and SEM observations.