Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Facility Location Placement Optimisation for Bagged Cement Distribution During the COVID-19 Pandemic
Get PDFThis study was based on a challenge that one of Thailand's cement companies encountered in 2021 as a result of fierce competition in the Northeastern region and falling market share during the COVID-19 pandemic. Without a doubt, the management of supply chains played an essential role in this issue. As a result, this research addressed the company's distribution strategy by attempting to determine a new location for the distribution centre to achieve two conflicting objectives at the same time, namely, minimising total transportation cost and maximising service level (delivery lead time reduction). For the problem at hand, a linear programming model was developed. Once different options were identified, the pros and cons of each approach were evaluated, and then the distribution strategy was altered to meet the actual conditions. It was discovered that changing distribution centres in some locations was a successful strategy for shortening delivery lead times with an opportunity to achieve a 22% improvement in service level while still controlling transportation expenses prior to arriving at the end customers not beyond the target at 15% increased from the current strategy
Face Synthesis and Partial Face Recognition from Multiple Videos
Get PDFSurveillance videos provide rich information to identify people; however, they often contain partial facial images that make recognition of the person of interest difficult. The traditional method of partial face recognition uses a database that contains only full-frontal faces, resulting in a reduction in the performance of recognition models when partial face images are presented. In this study, we augmented the database of full-frontal face images and synthesized two- and three-dimensional facial images. We designed a method for partial face recognition from the augmented database. To synthesize the two-dimensional (2D) facial images, we divided the available video images into groups based on their similarity and chose a representative image from each group. Then, we fused each representative image with a full-frontal face image using the scale- invariant feature transform (SIFT) flow, and augmented the original database with the fused images. To design a partial face recognition algorithm, we carefully evaluated the similarity between a set of video images from cameras and an image from the augmented database by counting the number of keypoints given by the SIFT. Compared to competitive baselines, the proposed method of partial face recognition has the highest face recognition rates in four out of six test cases on the widely used ChokePoint dataset, using most subjects (so-called subject group B) in the gallery. The proposed method also has recognition rates of approximately 22% to 72% on the test cases. The 2D face synthesis was found to outperform the three-dimensional (3D) face synthesis on a large subject group, possibly because the method of 2D reconstruction retains important facial features. The methods of augmentation and partial-face recognition are simple and improve the face recognition rate of traditional methods
CFD Investigation into Influences of a Transversely and Periodically Deforming Microchannel on Shear Stress Behavior in a Gut-on-a-chip Device
Get PDFOrgan-on-a-chip allows dynamic microenvironment of the actual organ to be simulated in vitro. In this study, the CFD simulation is used to investigate the behaviors of fluid flow and shear stress due to the effect of a transversely deforming membrane caused by the cyclic deformation of the microchannel sidewalls in a gut-on-a-chip device. The result reveals that the shear stress varies linearly along the length of the microchannel. The average shear stress per cycle is approximately three times greater than that of the stationary microchannel. The amplitude and frequency of the cyclic deformation also significantly affect the flow and shear stress behaviors. The highly dynamic shear stress in the gut-on-a-chip device could be one of the major factors that makes this kind of device more viable than the traditional static cell culture
A Review of Chaos Control Strategies for Tri-trophic Food Chain Ecological Systems
Get PDFThe existence of chaos in ecological models is quite obvious due to the presence of nonlinear terms. Controlling chaotic phenomena in ecological systems remains a difficult task due to their unpredictability, and thus chaos control is one of the main objectives for constructing mathematical models in ecology today. Our aim in this paper is to review chaos control strategies for the tri-trophic food chain models by using various ecological factors. The factors include additional food, prey refuge, the Allee effect, the fear effect, and harvesting. We establish the essential conditions for the existence of ecologically feasible equilibrium points in the food chain ecological systems and their local stability. This paper provides a unified overview of recent research on the chaos control of ecological systems. The theoretical results suggest a way to control populations of species in ecological systems for fishing and pest management in farming. Numerical examples are performed to justify and compare the theoretical findings through phase portraits and bifurcation diagrams
Investigation of PM2.5 Dispersion in Din Daeng District, Bangkok, Using Computational Fluid Dynamics Modeling
Get PDFDin Daeng is a small and densely populated district of Bangkok, with two major expressways and three main roads in the area. PM2.5 concentration in Din Daeng district often exceeds both the daily and annual standards of the National Ambient Air Quality Standards. Computational Fluid Dynamics (CFD) was applied to investigate the effects of the metropolitan characteristics and traffic volumes on the dispersion of PM2.5. The turbulent flow was analysed using the Standard k-ε model. There were two scenarios in this simulation study. One was to investigate the consequences of having the expressways. The other was to examine the influence of the city lockdown due to the COVID-19 pandemic. The presence of the expressways in Din Daeng district was demonstrated to increase PM2.5 concentrations by approximately 3.4 times compared to the case without the expressways. In addition, the city lockdown substantially reduced PM2.5 concentration by almost 49% compared to that during the normal period
Developing an Easy-to-Maintain UV Sanitizer Cabinet for Safe and Efficient Disinfection and Improved Hygiene Practices
Get PDFIn day-to-day life, people constantly come in contact with pathogens such as bacteria and fungi that can negatively impact human health, causing skin infections and foot-related issues. The aim of this research is to create an easy-to-maintain consumer level product utilizing UV-C to efficiently and effectively disinfect everyday household items to improve hygiene and general quality of life with a shortened time spent, less human labor required. Key design concepts are ‘minimal-design platform’ to keep things minimal and streamlined – highlighting uncomplicated forms plus having been made simpler, and ‘design for maintainability’ to achieve effective building’s performance - system functions in relation to designated criteria, easy-to-maintain, easy-to-access, convenient, and embracing a healthy lifestyle. Besides, the optional mobile application is added to the system for assisting users as a remote communication. The modules are adaptably made to future requirements while maintaining a stable usage cost throughout the building’s design life. For protecting users from UVC radiation leakage or emitted out from the cabinet (0 UVC leakage in the unit of mW/cm2 measuring by UVC light meter), the polycarbonate sheet is applied as a cover. The efficiency of UV sanitizer cabinet can be evaluated via structural performance (the maximum load that can be supported by rotary table is 1 kg.), bacterial culture test (the number of colonies decrease significantly to < 5%), and reliability of system (99.47%)
A Numerical Comparative Study of the Selected Cambered and Reflexed Airfoils in Ground Effect
Get PDFWhen a wing gets closer to the ground, the distortion of the flow and the dynamic air cushion have a positive influence on the aerodynamic characteristics. The vessels that utilize the advantage of this phenomenon in its operation are known as “Wing-in-ground effect craft” or WIG. However, the aerodynamic forces in ground effects are different from free stream flight, especially close to the ground. The center of pressure movement was found to be more complicated and varies with the ground clearance, angle of attack, and the airfoil profile which results in pitching instability in some cases. In this study, a numerical study comparing the aerodynamic characteristics of three commonly used airfoils and one reflexed airfoil in ground effect was carried out with the ground clearance ratio varying from 5% to 100% of the chord at a Reynolds number of 3 106 over a wide range of angles of attack from 0° to 20°. As expected, the high-cambered airfoil has the highest lift-to-drag ratio, but the stall occurs at a smaller angle of attack, especially at low ground clearance. It also has a greater center of pressure travel with a strong nose-down moment. The expected reduction of the movement of the center of pressure was obtained in the reflexed airfoil, resulting in better pitching stability at the expense of performance. The performance of the flat-bottom airfoils is compromised between the high-cambered and reflexed airfoil
Prediction of the Mechanical Behaviour of HDPE Pipes Using the Artificial Neural Network Technique
Get PDFActual statistics show that in recent years, more than 90% of the water distribution pipes installed in the world are made of plastic, exclusively polyethylene (PE). Due to the extensive use of these materials, it is necessary to have a good understanding of the mechanical properties of HDPE used for distribution system piping. For our study, we selected HDPE pipes as the material of choice. We then took a new approach to the analysis and prediction of mechanical properties, using new models based on Artificial Intelligence. In this paper, experimental tensile tests were conducted to obtain the mechanical properties of pipes. The first part of this work focuses on the mechanical tests, specifically tensile tests, while the second part centers on the numerical procedure for predicting the mechanical characteristics, a deep learning model was developed for prediction. The model was trained using a large dataset, including information on pipes. Specially designed deep learning architectures capture complex relationships and patterns in the data, enabling accurate predictions, Several ANN models were created to predict mechanical behaviour based on experimental data. We analyzed Bayesian regularization using MATLAB, an advantage of BR artificial neural networks is their ability to reveal potentially complex relationships. The results showed that the constructed prediction model is satisfactory since the M.S.E. value is nearly 0 (0.00023) and the value is close to 1 (0.99934). This study evaluates the advantages of our methodology by demonstrating the predictive power of an AI-based method and how well it predicts HDPE pipe behavior. The paper study will have significant effects on the water distribution and plastics industries
A Hierarchical Analytic Process Framework for Manufacturing System Improvement
Get PDFThis paper proposes a hierarchical analytic process framework to facilitate practitioners to determine improvement directions for a manufacturing system efficiently and systematically. The proposed framework analyzes current state performances of a manufacturing system by applying the knowledge of science of manufacturing systems which describe relationship control factors, performance measures, and improvement objectives. Then, concrete directions for improvements are suggested. The analysis process embeds the concept of diagnostic tree which makes it an easy-to-handle framework. Under the diagnostic tree concept, it decomposes the high-level business goal into successively low-level activities to give more comprehensive areas of improvement. The proposed framework comprises of three key elements: Operation Performance Measures (OPMs), Diagnostic tree (D-Tree), and Action guidelines. The OPMs are used in the D-Tree to determine improvement objectives. Then the Action guidelines suggest how to adjust control factors in a manufacturing system according to each improvement objective. The proposed diagnostic framework is demonstrated by Promodel simulation of a case study. The simulation model includes physical resources, flow lines, WIP, and replenishment signals of the case. By following the analytic process in the framework, the performance measures have shown improvements according to action guidelines and the result of improvements meets the requirement of a factory in the case study
The Potential of Polyacrylamide Polymer to Reduce Cracking During Wetting-Drying Cycles
Get PDFThis paper presents the potential of polyacrylamide (PAM) polymer to reduce cracking during wetting-drying cycles. Several experiments have been conducted to investigate PAM polymer in high plasticity silt soils to reduce soil cracks and increase soil strength properties. In this study, Polymer was mixed in soil with different PAM variations (0.2%; 0.4%; 0.6%, 0,8% and 1% by weight). The behaviour of each soil sample was measured by a thermal imaging technique and confirmed by microstructural analysis. The patterns of the soils captured by the camera were quantified using image processing. The experimental results show more cracks in the initial soils than in treated soils. This was confirmed by the SEM test, which showed pores of soil particles. The results also show the role of PMA in reducing the initial void ratio could lead to an increase in bearing capacity. The interaction between PAM and soil particles could also reduce the crack potential. This is because there is solid bonding within soil mass after PAM treatment. In general, this study demonstrates the potential of PAM to reduce cracking and increase soil strength, as well as bring new insights into the design and assessment of sustainable infrastructure under climate change