Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Human Motion Recognition Using Temporal Foot-Lift Features Extracted from a Small Number of Skeleton Data Frames and Multi Classifiers
Get PDFHuman motion recognition becomes an essential part of human–robot collaboration in many different applications such as robot-assisted smart factories, smart warehouse and smart transportation. However, there are still challenges in terms of spatial information and temporal information requirements. Aiming at reducing the number of frames and joint information required, temporal foot-lift features were introduced in this study. The temporal foot-lift features and five different classifiers were applied to recognize “Walking” and “Running” actions from four different human action datasets. Half of the data were trained and the rest were experimentally tested for performance evaluation. The results revealed that the proposed method can give up to 100% accuracy even using a small number of frames. Using KNN classifier and temporal foot-lift features can give the highest performance in recognition. The performance of proposed method was compared with existing methods’ performance. The skeleton joint information and temporal foot-lift features are promising features for real-time human motion action recognition
Micromechanical Behavior of Granular Materials Caused by Particle Shapes under Triaxial Loading
Get PDFThe mechanical behavior was investigated of 3 different particle shapes under different stress paths by setting various intermediate stress ratios. The method of 3D discrete element was applied to research the effect of particle shapes with aspect ratios of ellipsoids and spheres, with both specified by height/width values of 0.4, 0.6, and 1 under different intermediate stress ratios or b values. Each one was used with a single particle shape based on 16 different sizes and random rotation angles. All 3 samples were subjected to a limited isotropic pressure of 100 kPa prior to shearing and constant mean stress using a stress controller. Macro behavior was evaluated based on the stress and strain responses. Micro mechanisms were reported based on the coordination number together with the sliding contract fraction. The fabric tensor of the contact normal, normal contact, and tangential contact forces were examined for the various sample shapes during intermediate loadings of different stress ratios. It was found that anisotropic fabrics and the b values relative to the normal contact force were higher than for the contact normal for all shapes. Furthermore, at the peak stress of each stress path, the specific behavior of normal contact forces varied with the particle shape
Ocular Prosthesis Fabrication Scheduling Using Genetic Algorithm
Get PDFThis research examines an ocular prosthesis centre’s operation and incorporates scheduling decision techniques to optimise its fabrication. A customised eye prosthesis is a make-to-order product which involves several labour-intensive processes and inherently poses scheduling challenges. As a result, patients' fitment dates are appointed with extra time to account for potential delays. The objective of scheduling is to minimise both total completion time and tardiness. The methodology begins with a process review of the customised eye prosthesis fabrication and criteria. Subsequently, a Mixed Integer Linear Programming (MILP) model is formulated to solve the assignment and sequencing problems. It is found during this stage that computational time increases significantly as the number of orders increases. To solve this problem, a Genetic Algorithm (GA) is proposed to find a near-optimal solution in a reasonable computational time. Instances selected for experiment are based on characteristics of a tertiary hospital’s ocular prosthesis centre. Small instances are experimented to validate the proposed algorithm against the MILP model. The GA demonstrates near-optimal solutions with a variance of one percent, with reasonable computational time. Practical-size problems are subsequently solved using the proposed algorithm. In conclusion, the proposed GA yields satisfactory solutions with acceptable runtime for this application
Investigating Non-Newtonian Flow Characteristics of Polypropylene: A Computational Fluid Dynamics Study Utilizing COMSOL Multiphysics
Get PDFPolypropylene, a plastic used across industries showcases intricate flow behaviors essential for refining manufacturing techniques. This study utilizes fluid dynamics (CFD) to simulate the flow of polypropylene through an extrusion die focusing on how its viscosity alters under varying stress levels. With the intricate design of the extrusion die in mind the research seeks to comprehend viscosity changes, velocity patterns and pressure drops as molten polypropylene moves through the mold. The analysis divides the mold into three segments for examination: the inlet radial side, outlet radial side and a narrow pathway known as the choke point within the extrusion die. By employing COMSOL Multiphysics and the Carreau model researchers explore how adjusting pressure influences flow behavior and characteristics at these zones. Results indicate that heightened pressure results in increased flow rates as polypropylene tends to thin when stressed, leading to smoother flow conditions. Moreover, it is observed that viscosity profiles become more uniform with rising pressure levels. These findings provide insights into polypropylene properties, for optimizing mold design and polymer processing methods effectively. This interdisciplinary study combines expertise with applications to offer actionable guidance for enhancing polymer processing systems in terms of both design and operation
Green Synthesis Silver Nanoparticles (AgNPs) Utilizing Ari (Pithecellobium jiringa) Skin Waster Extract as a Bioreductor
Get PDFIn this study, silver nanoparticles (AgNPs) are widely applied as antibacterials and can be composited with polymers for automotive components. Pithecellobium jiringa epidermis waste extract contains several secondary metabolite compounds that can act as bioreductors to produce AgNPs. This research aims to synthesize silver nanoparticles (AgNPs) using P. jiringa epidermis waste extract as a bioreductant. The volume ratio of P. jiringa epidermis extract and 1 mM silver nitrate (AgNO3) solution is 3:7 at 25℃. Characterization of AgNPs using U-Visible (UV-Vis) Spectrophotometer, Particle Size Analyzer (PSA), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR), and X-Ray Diffraction (XRD) The results of UV-Vis, PSA, and SEM-EDX analyses, respectively, obtained AgNPs with an adsorbance of 2.121 at a wavelength of 430 nm at a reaction time of 96 hours, an average size distribution of 46.6 nm with a round shape, the element content of AgNPs, namely Ag, C, and O. wave number 2867.74 cm-1, and the C=C functional group at wave number 1613.18 cm-1
A Unified Optimization Model with Proportional Fairness and Robustness of Fuzzy Multi-Objective Aggregate Production Planning in Supply Chain under Uncertain Environments
Get PDFThis study aims to provide Decision Makers (DMs) with a framework for achieving long-term development of Aggregate Production Planning (APP) in a Supply Chain (SC). The contribution of this study is to consider both Proportional Fairness (PF) and robustness in the APP optimization processes, recognizing that overlooking fairness among the multi-objectives in APP may result in inequitable considerations due to different priorities. Neglecting robustness may yield unreliable and non-resilient outcomes in APP, particularly in uncertain situations where uncertain and vague information poses a challenge. To address these concerns, a unified proportional fairness and robustness optimization model is proposed by applying the principles of PF and Robust Chance-Constrained Programming (RCCP) to the conventional weightless objective optimization approach. The effectiveness of this approach is demonstrated through a case study of an APP problem in a SC with the objectives of minimizing total costs, minimizing fluctuations in workforce levels, and maximizing total values of purchasing under uncertain environments. The comparative analysis indicates that the outcome derived from the proposed approach outperforms the results of both traditional weightless and fairness approaches, particularly in enhancing fairness and robustness in the APP
Effects of Weave Pattern on Filtration Performance of Woven Filter Cloths by Computational Fluid Dynamic Modeling
Get PDFOutdoor physical activities are essential for maintaining a healthy lifestyle, but they can also expose individuals to harmful air pollutants such as particulate matter. Particulate matter, especially those with a diameter of less than 10 µm (PM10), can penetrate deep into the lungs and cause adverse health effects such as respiratory diseases, cardiovascular diseases, and even premature deaths. Consequently, masks are essential while outside with high PM pollution. Additionally, the COVID-19 pandemic has made it necessary for people to wear masks as a protective measure against the virus while engaging in outdoor activities. However, not all masks provide adequate protection against both the virus and particulate matters. This study aimed to investigate the effect of weave patterns on the filtration performance of woven filter cloths using Computational Fluid Dynamics (CFD) simulations. A laminar-flow model was applied due to low Reynolds number of the face velocity. Specifically, the study focused on PM10. The filtration process was examined in a relation to three weave patterns: plain weave, twill weave, and satin weave, using the CFD model. The Discrete Phase Model (DPM) was used for simulating the particulate matter trajectories. The numerical model was validated with the data from Konda et al (2020) [19]. The results showed that the twill and satin weaves had higher filtration efficiencies than the plain weave. Finally, the findings of this study will be used to guide the manufacturing of masks that are suitable for protecting individuals from the dust and viruses while exercising
The Study on Annealing Temperature and Rolling Speed Effects in Relation with Microstructure, Mechanical Properties and Surface Quality of Hot Rolled S450J0 Steel
Get PDFThis study investigates the impact of annealing temperature and rolling speed on the microstructure, mechanical properties and surface quality of hot-rolled S450J0 structural steel, focusing on the production of HP 305x305x223 kg/m H-beams. Various annealing temperatures and rolling speeds were utilized to determine their effects on the product quality. Results indicate that annealing temperature significantly influences mechanical properties, with higher temperatures increasing yield and tensile strengths but potentially reducing elongation and impact toughness. In contrast, variation in rolling speed has minimal impact on mechanical properties due to the consistent finishing temperatures. Microstructure analysis reveals that higher annealing temperatures lead to smaller grain sizes, while lower temperatures result in clear ferrite grain alignment. Surface defects on steel surfaces, including crack patterns, are shaped by both annealing temperature and rolling speed. SEM analysis confirms the depth and characteristics of surface cracks, aligning with optical microscope observations. Overall, optimizing annealing temperature and rolling speed is essential for minimizing surface defects and enhancing product quality during the hot rolling process of H-beams
The Role of Energy Density in Phase-Microstructure Evolution and Mechanical Properties of Ti-Zr-Cu Alloys Fabricated by Laser Powder-Bed Fusion
Get PDFLaser powder-bed fusion (L-PBF) additive manufacturing technique offers significant advantages in fabricating Ti-Zr-Cu alloys by enabling precise control over microstructure through process parameter variation. This study investigates the impact of energy density on phase formation, microstructure evolution, and mechanical properties of Ti-Zr-Cu alloys produced from blended elemental powders. By adjusting laser scan speeds to achieve different energy densities, the study reveals that high energy densities result in homogeneous β-(Ti,Zr) phases, while lower energy densities lead to incomplete melting, phase segregation, and inhomogeneous microstructures. Advanced characterisation techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD), were utilised to analyse phase composition and microstructural transformations. Vickers hardness testing demonstrated a correlation between energy density and mechanical properties, with higher energy densities improving overall material hardness. The findings offer valuable insights into optimising L-PBF process parameters for enhanced performance in additively manufactured Ti-Zr-Cu alloys, providing a pathway for advanced applications in biomedical and structural components
The Conditions and Suitable Coupling Speed to Create a Train Convoy: A Train Movement under the Virtual Coupling Control
Get PDFA new signaling control called “Virtual Coupling System” (VCS) has been developed and proposed for increasing rail line capacity without construction of new lines. Coupling trains proceeding as a train convoy increases the headway (time space) in front of the convoy. Receiving the benefit from an increase in headway, more trains can be inserted to proceed along the same line increasing capacity. However, it is not clear when trains should be coupled as a train convoy and how a train convoy is built.
In this article, the objective is to provide the conditions to determine whether a train convoy should be built, conditions to determine the number of trains that should be coupled into the same convoy, and the equations to calculate the suitable speed that trains should proceed for coupling into the train convoy. According to the simulated train movement based on the proposed approach, the line capacity is significantly increased as an additional train can be inserted. The headway in front of a train convoy is increased allowing an additional train to be inserted into the same line. In addition, it is ensured that trains can proceed as a train convoy safely, in which the separation distance between successive trains is longer than the minimum safe distance required for the VCS