Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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1223 research outputs found
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Finite Element Analysis-Based Pre-operative Application for Biomechanical Evaluation of a Locking Plate Used in Reconstruction After En Bloc Resection of a Stage 3 Giant Cell Tumor of the Distal Radius
Full text linkThe subject of the study was a pre-operative application involving the use of a locking plate in reconstruction after en bloc resection of a Stage 3 giant cell tumor from the distal radius in a 60-year-old male patient. The essence of the application was the use of finite element analysis to determine stresses in and deformations of the bone, plate, and screws. A model of the distal radius was constructed using CT data from a specific patient and the type and magnitude of the loading on the system were those experienced by the patient during the post-surgery period. The boundary conditions used were consistent with the aforementioned loading. Several parameters were selected as adjustable parameters in the application builder toolbox. The maximum deformation of the plate was 5.05 mm. The maximum von Mises stress was 75.06 MPa in the bones and 1,123.35 MPa in the plate. A loosened screw was located at the proximal zone of the plate, with the maximum pull-out force in the screw being 679.35 N. This was comparable to the value obtained from experimental tests, thus validating the FEA results. The maximum von Mises stress in the system exceeded the yield strengths of the bones and of the plate material (Ti-6Al-4V). The proposed application may be used by orthopedic surgeons to visualize the biomechanical performance of the bones-locking plate-screws system and to guide patients for loading actions to avoid or limit in the post-surgery period
Optimization of Bar Cutting Lists in Reinforced Concrete Columns Utilizing the Particle Swarm Optimization Algorithm: A Case Study of a High-Rise Building
Full text linkIn the construction of reinforced concrete structures, rebar bending and cutting lists are commonly developed. However, in practice, engineers often develop them based on ease of design. This involves specifying splicing patterns manually, rather than using optimization techniques. To address this issue, a framework for optimizing rebar cutting and splicing patterns using Particle Swarm Optimization (PSO) is proposed in this study. Two areas of a high-rise building were used as a case study to demonstrate the practical application. The framework first organizes the columns by reinforcement patterns before further subdividing the column categories’ rebars by diameter and end patterns. Next, it randomizes splicing positions to serve as initial positions for PSO. Then, the corresponding cutting lengths are calculated and used for waste calculation. These processes are iterated to minimize waste. The results showed a significant reduction in waste across both areas, from 13.86% to 2.88%, compared to the as-built bar cutting list. This highlights the effectiveness of the framework in improving material efficiency and supporting sustainability. To validate practicality, the cutting and bending processes using machinery integrated with a QR code reader at a factory were demonstrated. This ensures the precise execution of the optimized list and enhances its robustness in real-world applications
Data-Driven Solutions for Backcalculating Elastic Moduli of Flexible Pavements from FWD Test
Full text linkTraditional methods for calculating pavement layers elastic moduli from falling weight deflectometer (FWD) tests often rely on computationally intensive iterative processes and lack struggle to capture complex variable relationships. This article highlights the utilization of machine learning (ML) algorithms, which include artificial neural networks (ANN), long-short-term memory (LSTM), and random forests (RF), to predict the elastic moduli of multi-layered flexible pavement based on FWD test. All ML algorithms were developed using synthetic databases derived from the exact stiffness matrix scheme, which was employed for the analysis of multi-layered pavements under axisymmetric surface loading. The development of ML models involves preprocessing of data, hyperparameter optimization, and performance evaluation. The input variables consist of the FWD surface deflections, the magnitude of applied loading, and the layer thicknesses, while the output variables represent the predicted layered elastic moduli of the pavement structure. The ANN and LSTM models capture complicated relations more effectively than the RF model in the backcalculation of the layered elastic modulus based on the FWD test. Among the two, LSTM achieves higher accuracy, with the average values across all layer moduli of R2 and MAPE being 99.04% and 2.41%, respectively, in the test set. The applicability of LSTM model is further demonstrated by comparing with the backcalculated elastic modulus based on the FWD field experiments performed on the infrastructure of roads in Thailand. Furthermore, a sensitivity analysis reveals that deflections near the center of loading predominantly impact the predictions of upper layer moduli, while the moduli of lower layers are influenced by deflections across all geophones
Microwave-Assisted Green Synthesis of Silver Nanoparticles (AgNPs) Using Pithecellobium Jiringa Epidermis Extract: Optimization of Irradiation Time And AgNO3 Concentration
Full text linkSilver nanoparticles (AgNPs) are widely utilized due to their antimicrobial properties and potential applications in biomedical and environmental technologies. However, environmentally friendly synthesis methods with more efficient reaction times are needed to avoid the use of hazardous chemicals and to reduce lengthy synthesis durations. This study aims to determine the optimal irradiation time and AgNO3 concentration for producing AgNPs using Pithecellobium jiringa (P. jiringa) seed coat extract as a bioreductant with the microwave irradiation method. The seed coat of P. jiringa contains phytochemical compounds capable of reducing Ag⁺ ions into silver nanoparticles. Microwave irradiation was employed to accelerate the synthesis process by enhancing reaction homogeneity and efficiency. AgNO3 concentrations of 1 mM, 3 mM, and 5 mM were tested, with 14 minutes identified as the optimal irradiation time. Characterization results showed that the average size of AgNPs at 1 mM AgNO3 concentration was 96.9 nm, while at 3 mM and 5 mM concentrations, particle sizes significantly increased to 521.7 nm and 3874.5 nm, respectively, due to agglomeration. UV-Vis analysis confirmed the formation of AgNPs with absorption peaks in the wavelength range of 400–450 nm. This study indicates that the optimal conditions for synthesizing small and stable AgNPs are 14 minutes of irradiation and 1 mM AgNO3 concentration
An Empirical Study of Grid Fins Aerodynamic Performance in Low-Subsonic Flight
No full textDeploying payloads from aerial platforms at low altitudes poses significant challenges, particularly in maintaining an accurate freefall trajectory. Traditional fin designs are often used in dropped payloads at low altitudes. However, these designs frequently fail to preserve the intended trajectory, reducing precision and effectiveness. This challenge is particularly evident in high-wind conditions, where achieving landing precision or maintaining a desired trajectory becomes more difficult. To address these limitations, alternative fin designs, such as grid fins, offer a promising solution due to their unique aerodynamic properties. The current study investigates the aerodynamic performance of grid fins in low-subsonic flight, focusing on their application in drone-dropped payloads. The primary objective is to assess how different grid fin design parameters affect aerodynamic performance. Experimental analyses are conducted through subsonic wind tunnel testing of various grid fin designs. The study highlights the differences in aerodynamic performance resulting from grid count variations and the grid members' horizontal versus diagonal placement. The experimental results indicate that grid fins with a diagonal configuration outperform their horizontal counterparts with the same grid numbers and dimensions. The findings reveal the presence of an optimal configuration, achieving a peak lift-to-drag (L/D) ratio of approximately 1.99, compared to 1.4 for the least optimal design
Developing Prototype of Piping Design Knowledge Management Systems in the Oil and Gas Industry
No full textThe limited acceptance of existing knowledge management systems within organizations necessitates enhancements to improve their effectiveness. This study addresses this issue by developing and evaluating a prototype of a piping design knowledge management system in the oil and gas industry. Utilizing a Design Science Research (DSR) methodology, the research identified key system requirements through theoretical analysis and structured interviews with representative users across various functional roles. Based on these insights, a prototype emphasizing knowledge retrieval and creation functionalities was developed and empirically tested against the existing system. The results indicate significant improvements, including increased success rates, enhanced system usability (with average system usability scale scores rising from 36.10 to 78.20), and high technology acceptance (81%). Furthermore, the new system eliminated lostness, reduced average knowledge retrieval time from 52.68 to 46.51 seconds, and significantly decreased knowledge creation time from 229.81 to 93.68 seconds. These findings demonstrate the potential of the proposed system to enhance organizational performance, suggesting broader applicability across engineering departments
Effect of Macro, Micro, and Nano Lime Particles on the Stabilisation of Expansive Soils
Full text linkThis paper explores the potential of lime to mitigate the shrinkage and expansion properties of expansive soils through plasticity index (PI) testing. Expansive soils are prone to significant volume changes due to moisture fluctuations, which can substantially damage building structures. A series of experiments were conducted to evaluate the effectiveness of lime in these soils, focusing on three distinct particle sizes: macro, micro, and nano. The research examined the impact of varying lime concentrations—1%, 2%, and 3% by weight of soil—on these different soil types. The findings suggest that finer lime particle sizes are more effective in reducing the initial void ratio of the soil, thereby enhancing its bearing capacity. The interaction between smaller lime particles and the soil matrix promotes improved bonding within the treated soil mass, reducing the likelihood of cracking. Overall, this study highlights the significant role of lime particle size in enhancing soil stability and strength
Recovery of Waste Engine Oil by Pyrolysis Distillation Process
Full text linkThe aim of this research is to study the feasibility of recovering waste engine oil (WEO) into diesel-like fuel using a novel two-stage reactor. The system increases the oil yield and quality, representing a considerable progress in hazardous waste management. The study examines optimal process conditions, including pyrolysis and distillation temperatures, carrier gas flow rates, and the effects of three catalysts: Fe2O3, Na2CO3, and bentonite. The results show that the temperature directly affects the pyrolysis process, with thermal cracking being the main reaction. Increasing the carrier gas flow rate improves the heat transfer capacity of the feed oil, thereby enhancing oil breakdown in the reaction. The optimal conditions for producing pyrolysis oil were determined as a pyrolysis temperature of 400°C, a distillation temperature of 250°C, and a carrier gas flow rate of 30 mL/min. Under these conditions, the produced pyrolysis oil had the highest combined composition of naphtha, kerosene, and gas oil, with its specific gravity and viscosity falling within the diesel standards range, although the flash point remained below the standards. Under the examined catalysts, Na2CO3 preferentially reacted with large hydrocarbon molecules, resulting in pyrolysis oil with heavy oil content. The use of Fe2O3 significantly reduced the sulfur content in the oil, while bentonite had a greater selectivity for naphtha. The study particularly shows the integration of re-distillation as an additional refining step, which has successfully improved the flash point to meet diesel fuel standards. These results demonstrate the potential of this approach to recycle hazardous waste into valuable fuel products
A Review of Mechanical Element Design of Lunar Greenhouse for Long-term Space Mission
Full text linkHumans have been learning to survive in space with the aim of prolonging the periods of missions. To be able to stay longer, the resources for a living are important for the crews. However, the payloads brought into space should be restricted because of the mass and cost limitations, so it is not often possible to transport limited resources like water or food from Earth to the Moon. In recent years, there has been a concept of a Moon Village established for humans to be able to stay in space longer. Consequently, a greenhouse module was proposed to meet the needs and was designed with concepts of the Moon’s environment and Environmental Control and Life Support Systems (ECLSS). This review paper includes brief details of the greenhouse module design and the two main subsystems of a lunar greenhouse: agricultural subsystems and environmental control subsystems in mechanical engineering aspects. In addition, comparisons of the advantages, disadvantages, and challenges of the three designs of lunar greenhouse modules are provided since each design had its own characteristics. Thus, the engineers should choose a proper design by considering the requirements and limitations regarding the mission. Also, this review paper can further expand knowledge of designing greenhouse modules on the lunar surface and improving the subsystems in the greenhouse module in the engineering field
Analysis of an RC Flat Roof ECM under an Accidental Explosion from an Adjacent ECM
Full text linkAn earth-covered magazine (ECM), a military structure used to store ammunition and explosives, is usually constructed in groups. An accidental explosion in one of the ECMs in the group can lead to the formation of a chain explosion. Therefore, an ECM needs to be designed to protect its contents and prevent the propagation of an explosion to adjacent ECMs. In this study, the behavior of a one-third scaled reinforced concrete (RC) flat roof ECM was examined under an internal explosion from the adjacent ECM by using computational simulation. A comprehensive 3D numerical model capable of simulating detonation, blast wave formation, blast wave propagation, and fluid-structure interaction was developed. The validated constitutive material laws and equation-of-state (EOS), appropriate boundary conditions, and Arbitrary Lagrangian Eulerian (ALE) formulation were adopted in the model. The numerical analysis showed that the designed ECM was able to maintain structural integrity without significant damage to the RC walls and roof during the explosion from the adjacent ECM. Moreover, the pressure inside the exposed ECM remained unaffected during the accidental explosion, ensuring the safety of its contents and the subsequent propagation of explosions. Overall, the findings of this study are useful for designing safe and efficient ECM structures