Journal of Engineering and Technological Sciences

The Effect of Ignition Timing on Combustion of Ammonia/Ethanol Mixtures in Spark-Assisted Compression Ignition Engine with a Sub-chamber

2025-06-30T11:49:57+07:00

Carbon dioxide (CO2) is the primary contributor to greenhouse gas emissions. Ammonia (NH3) has emerged as a promising alternative fuel due to its high energy density, ease of transportation, and carbon-free molecular structure. However, its practical application is challenged by slow combustion characteristics and high ignition temperatures. This study investigates the combustion behaviour of ethanol-ammonia mixtures using a high-compression-ratio engine (17.7:1) equipped with a sub-chamber. The engine operated at a constant speed of 1000 rpm. Ammonia energy ratios of 40%, 50%, and 60% were tested across ignition timings of 0°, 2°, 4°, 6°, and 8° crank angle (CA) before top dead center (BTDC). Results indicate that advancing the ignition timing increases in-cylinder pressure and heat release rate while reducing combustion duration. Lower ammonia energy ratios yielded higher thermal efficiency. Conversely, higher ammonia content and advanced ignition timings led to increased NOx emissions.

Developing Carbon Nanofibers from Gnetum Gnemon Linn Pericarp Using Dual Activators KOH And Melamine as Innovative Electrode Materials for Supercapacitors

2025-08-12T15:53:03+07:00

Synthesis of carbon nanofibers from Gnetum gnemon Linn (GP) biomass with dual activators, KOH and melamine, offers a potential approach for high-performance supercapacitor electrodes. This study evaluated the preparation of GP-based carbon nanofibers through single and double activation, with varying melamine masses of 0.1, 0.3, and 0.5 g at 0.3 M KOH. The pyrolysis (integrated carbonization and physical activation) occurred at 600°C in N₂ and 800°C in CO₂ atmospheres. The material was activated using 0.3 g of melamine in 0.3 M KOH to produce abundant and highly amorphous nanofiber structures. These characteristics contributed to the high specific capacitance of 400 F/g at a scan rate of 1 mV/s and an energy density of 17 Wh/kg at a power of 465 W/kg. These results demonstrated the synergistic effect of melamine and KOH in increasing the active surface area and structural conductivity. This finding confirms the potential of GP biomass that has not been optimally utilized as a sustainable precursor for energy storage applications, especially supercapacitors.

Crashworthy Structure Analysis of Indonesia's First High-speed Train Trailer Made from Aluminum Extrusion

2025-08-19T10:03:03+07:00

In the development of high-speed trains, evaluating the crashworthiness of passenger car structures is essential, particularly in the vestibule area which designed to absorb impact energy. When constructed entirely from aluminum extrusion, the vestibule exhibits high stiffness and uncontrolled energy absorption, resulting in excessive deceleration during collisions. This study investigates the crashworthiness of the vestibule structure in Indonesian high-speed train trailers, referencing EN 15227/SNI 8826 and 49 CFR 238 standards. A numerical analysis was conducted using ANSYS LS-DYNA, examining four structural configurations: a full aluminum extrusion model referred to the rear end structure of the HST locomotive, and three alternatives incorporating structural beams in the roof, floor, and modified floor areas. Simulations involved train collisions with a rigid wall at regulated speeds, using aluminum 6005A-T6 modeled with the Johnson-Cook material model to account for high strain rates. Results showed that the full aluminum design produced excessive deceleration and failed to meet EN 15227/SNI 8826 criteria. In contrast, the modified floor frame design achieved the lowest crash force and deceleration, controlled energy absorption, no survival space reduction, and compliance with EN 15227/SNI 8826, though it did not meet 49 CFR 238 deceleration limits due to full vestibule deformation. These findings offer valuable insights for manufacturers seeking to enhance the crashworthiness of high-speed train passenger cars.

Influences of Groove Geometries on Bend Radius and Springback in V-Bending

2025-08-11T17:16:42+07:00

Investigation of the V-bending process with the effect of V-grooving insert geometries is performed through finite element analysis within ANSYS LS-DYNA. Different V-groover geometries are tested to evaluate the effect on the final bent angle and bent radius of the sheet metal part, with the objective of obtaining the minimized bent angle and bent radius results. It is also observed that the corner radius of the V-groover has a major influence on the bent angle and bent radius. Due to the removal of material in the bending region, which reduced the bending resistance, an increase in the corner radius results in a decrease in both the bent angle and radius. The shape of V-groover also affects the bending results, with variations in geometries leading to variations in both bent angle and radius. When the cutting cross-sectional area is kept constant, the bent angle shows minimal variation, while the bent radius steadily increases with the V-groover angle, reaching its maximum at 90 degrees.

Multi-criteria Decision Making to Improve Displacement Amplification Ratio of an Amplifying Compliant Mechanism Flexure Hinge

2025-08-12T11:13:54+07:00

Multi-criteria decision-making methods including the Extended Additive Ratio Assessment (EAMR), Simple Additive Weighting (SAW), Weighted Aggregated Sum Product Assessment (WASPAS), and Evaluation based on Distance from Average Solution (EDAS) were employed in conjunction with the Taguchi method and finite element method (FEM) to optimize the displacement amplification of an amplifying compliant mechanism utilizing flexure joints. Initially, design variables for the compliant mechanism amplifier were selected. Minitab software was utilized to generate 27 experimental scenarios, and SolidWorks was employed to design 27 models of compliant mechanisms amplifier with flexure hinges. The stress and displacement of each design were estimated by FEM in ANSYS. The optimal mechanism was identified based on the largest displacement criterion as well as ensuring the smallest stress, as determined through the multi-criteria decision-making techniques and validated using the Taguchi method, variance analysis, and 3D surface plots. The predicted outcomes from the optimization methods are compared with FEM results for verification. For the EAMR method, the predicted and optimal values are 0.742046 and 0.74968, respectively. The SAW method yields values of 0.88684 (predicted) and 0.89210 (optimal), while the WASPAS method produces 0.8432 and 0.8481. The EDAS method results are 0.7978 (predicted) and 0.8187 (optimal). For displacement (Di), the predicted and optimal values are 0.65269 and 0.65238, respectively, and for stress (St), they are 49.3398 and 48.7950. In all methods, the deviation between predicted and optimal values remains under 3%. The resulting displacement amplification ratio (DAR) of the final mechanism is 65,237.

Classifying Rockburst Events and Intensity in Underground Mines using Grey Wolf Optimization–Support Vector Machine and Extreme Gradient Boosting

2025-10-20T08:35:33+07:00

Rockbursts are destructive accidents that often occur in underground mines. With the advancement of technology, machine learning has emerged as an alternative solution that can be used for rockburst mitigation. In this research, we classify rockburst events and their intensities in underground mines using two machine learning models: grey wolf optimization–support vector machine (GWO–SVM) and extreme gradient boosting (XGBoost). Rockburst events are classified into two categories: Existent and None. Meanwhile, the intensities are classified into three categories: weak, moderate, and strong. The implementation used 476 cases of rockbursts with six variables: maximum tangential stress, uniaxial compressive strength, uniaxial tensile strength, stress coefficient, rock brittleness coefficient, and elastic strain index. Both models can better predict the “Existent” rockburst class with a “Weak” intensity compared with the other intensity classes. The performances of the models are evaluated using different proportions of training data, ranging from 50% to 90%. Both models have the same performance for rockburst event classification with 97.53% accuracy, 0.9444 precision, 0.9846 recall, and 0.9628 F1-score. Meanwhile, for intensity classification, XGBoost outperforms GWO-SVM with its 88.24% accuracy, 0.8413 precision, 0.9137 recall, and 0.8651 F1-score.

Electrochemiluminescence sensor based on GDYO-QD@M-ZnO and its application in the detection of free radicals and antioxidants

2025-08-11T10:48:21+07:00

In view of the problems such as low luminous efficiency, poor stability and weak anti-interference ability of traditional electrochemiluminescence sensors, this study prepared graphdiyne oxide quantum dots by acid oxidation method and synthesized metal-organic skeleton derived zinc oxide by high-temperature calcination. The two were combined to construct a new ECL sensor. It is used for detecting free radicals and antioxidants such as vitamin C, trixerutin, and metformin hydrochloride. The results showed that GDYO-QD was successfully combined with M-ZnO. The constructed sensor has excellent electronic transmission ability, and the electrochemiluminescence signal is significantly enhanced compared with a single material, and has good detection performance for the target analyte. This study provides new ideas and practical tools for developing high-performance electrochemiluminescence sensors and effectively detecting free radicals and antioxidants.

Sustainable thermal insulation of geopolymer blocks using solid waste: palm oil ash and palm oil clinker

2025-05-26T10:22:35+07:00

This paper has analyzed the thermal insulation of geopolymer blocks prepared using palm oil ash (POA) with the addition of alumina powder (AP) and field Para rubber latex (FPRL). The block samples were set up to use 3 and 5 channels and channel width of 2 and 4 mm each with geopolymer binder as POA (containing 5% FPRL and 0%, 2.5%, 5%, 7.5%, and 10% AP) and POC as fine aggregate. The compressive strength, water absorption, bulk density of the geopolymer mortars and thermal conductivity of geopolymer blocks were explored. The AP and FPRL had minimal impact on the compressive strength of the geopolymer mortars and the greater the amount of AP the less water was absorbed. Thermal conductivity of 4 mm wide channel geopolymer blocks was lower than that of 2 mm wide channel blocks and 5 channels blocks had lower thermal conductivity in comparison to 3 channel blocks. The geopolymer blocks had low thermal conductivity relative to the commercial concrete blocks. This study offers valuable information to the application of geopolymers made of POA with FPRL and AP to produce geopolymer materials, POC as a fine aggregate to produce green building materials with enhanced thermal insulation.

The Initial Development of Integrated Add-On Tele-Ultrasonography for Monitoring the Health of Pregnant Women and Fetuses in the Community Health Centers in Indonesia

2025-08-29T10:41:24+07:00

Maternal health and fetal growth in rural areas require special attention due to limited access to adequate healthcare systems. Early detection of fetal health conditions can be achieved using B-mode ultrasonography (USG). However, expectant mothers in these regions often lack regular to regular check-up, even when healthcare facilities are available there may not be trained professionals available to analyze the B-mode images obtained in the Community Health Centres. To address this gap, a tele-USG system was developed that allows healthcare workers in remote areas to operate basic USG equipment and transmit real-time images to specialist doctors at higher-level healthcare facilities. During system development, a general-purpose USG phantom was used to test parameters: penetration depth, geometric accuracy, focal zone, and axial and lateral resolution. Testing confirmed that both USG and laptop used for streaming produce reliable and accurate results. A slight geometric representation differences of 2.74% (approximately 1 cm per target) was observed, attributed to dimensional distortion between devices with different monitor sizes. In geometric accuracy tests, five out of eight vertical and six out of seven horizontal targets were successfully detected. The smallest variation of 0.028 mm occurred at 5 MHz frequency, demonstrated high precision focal zone measurements. The axial resolution ranged between 0.25-0.5 mm, while lateral resolution ranged from 1.0-2.0 mm, indicating strong capability for fine-detail imaging. Overall, the system exhibited high sensitivity and excellent imaging performance, offering a promising solution to enhance maternal and fetal healthcare challenges faced by rural communities in Indonesia through accessible real-time diagnostic support

Sensitive Detection of Rhodamine B Using Surface Enhanced Raman Spectroscopy with a BiFeO3 based Substrate

2025-07-08T14:28:01+07:00

Surface-Enhanced Raman Spectroscopy (SERS) is a highly effective technique for detecting trace amounts of molecular species. However, the widespread use of conventional noble metal substrates is limited by high fabrication costs and scalability issues. Perovskite materials have recently emerged as promising alternatives, though many are lead-based and pose environmental risks. In this study, we present a lead-free bismuth ferrite (BiFeO₃) perovskite synthesized via the sol–gel method as a novel SERS substrate for the detection of Rhodamine B, a toxic dye commonly used illicitly in food products. Comprehensive characterization using X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and UV-Visible Diffuse Reflectance Spectroscopy confirmed the successful formation of a single-phase rhombohedral structure with a direct bandgap of 2.1 eV, indicating strong visible-light absorption. The BiFeO₃ substrate demonstrated effective SERS performance, facilitating a detection of Rhodamine B at concentrations as low as 10 ppm. These results highlight the potential of lead-free BiFeO₃ perovskites as practical and environmentally friendly alternatives to noble metals for SERS-based detection of hazardous dyes and other environmental contaminants.