Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
Not a member yet
1223 research outputs found
Sort by
A Development of Computer Aided Program for Aluminium Die-Casting Mold Design
Get PDFIn each stage of design, aluminium die-casting mold design is considerate many factors and conditions. The design requires some experiences with trial-and-error platform that causes the problems such as misrun, cold shut, cold shot, penetrations or instability stage during or after molding process. Proposed in this research is about the development of Computer Aided Program to support aluminium die-casting mold design to select and estimate the initial state values under the same standard condition requirements. Before starting a mold design, the C# language is asked to construct the platform that soothes and is insightful or applicably useful in a content database of reference theory, equations and principles including mold parameters. After identifying the proper input conditions of the mold design, the analysis of die casting MAGMASOFT is performed to verify the conditions of the material flow according to the suggested parameters. The simulated results can be considered as the guideline for supporting mold designer where the essential values of mold dimensions and the cold chamber type injection conditions are obtained as easy-to-access graphical images and numerical values. Applying this developed program can help to reduce time spent for mold designing stage with less defects occurred on the obtained cast parts
Permanent Deformation Behavior under Repeated Load of Recycled Material Stabilized with Bitumen Emulsion
Get PDFCold in-place recycling (CIR) with bitumen emulsion is a method for enhancing resistance to permanent deformation damages of flexible pavement. The objective of the study was to examine the permanent deformation behavior of a bitumen-stabilized material (BSM) subjected to repeated loads. To achieve this, the aggregate was derived from reclaimed asphalt pavement and reclaimed crushed rock in the ratio of 25:75 mixed with 2% or 3% bitumen in emulsion and 1% Portland cement (of the total aggregate weight). After that, the specimens were subjected to repeated loads following the EN13286-7 method. The results were as follows. At the compressive deviatoric stress level of 550 kPa, All of BSM specimens with 2% and 3% bitumen exhibited the plastic shakedown equilibrium pattern of permanent deformation after 1,000,000 cycles of repeated loads and their permanent strain were less than 0.6%. The results also indicated that once the permanent strain rate decreased to 0.004 microstrain/cycle or lower, the BSM became stable in the plastic shakedown state. The findings in this study may serve as guidelines for designing pavement rehabilitation with BSM to prevent permanent deformation caused by traffic loads
GA-Based Optimization for Multivariable Level Control System: A Case Study of Multi-Tank System
Get PDFThis paper presents a systematic way to determine the trade-off optimized controller tunings using computation optimization technique for both servo and regulatory controls of the Multi-Tank System, as one of the applications under the multivariable loop principle. The paper describes an improved way to obtain the best Proportional-Integral (PI) controller tunings in reducing the dependency on engineering knowledge, practical experiences and complex mathematical calculations. Relative Gain Array (RGA) calculation justified the degree of relation and the best pairing for both interacted control loops. Genetic Algorithm (GA), as one of the most prestigious techniques, was used to analyze the best controller tunings based on factor parameters of iterations, populations and mutation rates to the applied First Order plus Dead Time (FOPDT) models in the multivariable loop. Amid simulation analysis, GA analysis’s reliability was justified by comparing its performance with the Particle Swarm Optimization (PSO) analysis. The research outcome was visualized by generating the process responses from the LOOP-PRO’s multi-tank function, whereby the GA tunings’ responses were compared with the conventional tuning methods. In conclusion, the result exhibits that the GA optimization analysis has successfully demonstrated the most satisfactory performance for both servo and regulatory controls
Mechanical Diaphragm Structure Design of a MEMS-Based Piezoresistive Pressure Sensor for Sensitivity and Linearity Enhancement
Get PDFAn improved design of the micro-electromechanical system (MEMS) piezoresistive pressure sensor with a combination of a petal edge, a beam, a peninsula, three cross beams and a center boss is proposed in this work for an operating range of low pressure in order to improve the sensor performance, i.e. the sensitivity and the linearity. The finite element method (FEM) is utilized to predict the stress and the deflection of the MEMS piezoresistive pressure sensor under the applied pressure of 1-5 kPa. The functional forms of the longitudinal stress, the transverse stress and the deflection are formulated by using the power law and then are used to optimize the geometry of the proposed design. The simulation results show that the proposed design is able to produce the high sensitivity up to 34 mV/kPa with the low nonlinearity of 0.11% full-scale span (FSS). The nonlinearity error is lowered by the proposed design of the peninsula, three cross beams and the center boss. The sensitivity is enhanced by increasing the petal edge width. The sensor performance of the proposed design is also compared to that of the previous design in the literature. The comparison reveals that the proposed design can perform better than the previous one
SCAPS Numerical Analysis of Solid-State Dye-Sensitized Solar Cell Utilizing Copper (I) Iodide as Hole Transport Layer
Get PDFHere, numerical study of solid-state dye-sensitized solar cell (SSDSSC) with Copper (I) Iodide as a hole transport layer was investigated using SCAPS-1D simulation software. The complete simulated device structures in this project are composed of FTO/TiO2/N719/CuI/Ni. Several key parameters of HTL such as layer thickness, doping concentration, working temperature, and interface defect have been analysed to obtain the highest efficiency for SSDSSC as well as the influence of back contact. The incorporation with various ETLs such as TiO2, ZnO, and SnO2 were also studied. The results show that SSDSSC with back contact yields a better performance due to low HTL thickness compared to without back contact. In addition, it can also be proved that TiO2 as ETL obtained the best efficiency up to 5.6%. Further investigation also found that combining optimized CuI and TiO2 parameters with a perovskite layer would increase cell efficiency to nearly 30%, higher than previously reported devices. The proposed parameter structure may trigger the temptation for the use of CuI as HTL in solar cell application
Efficient Decision Trees for Multi-class Support Vector Machines Using Large Centroid Distance Grouping
Get PDFWe propose a new technique for support vector machines (SVMs) in tree structures for multiclass classification. For each tree node, we select an appropriate binary classifier using data class centroids and their in-between distances, categorize the training examples into positive and negative groups of classes and train a new classifier. The proposed technique is fast-trained and can classify an output class data with a complexity between O(log2 N) and O(N) where N is the number of classes. The 10-fold cross-validation experimental results show that the performance of our methods is comparable to that of traditional techniques and required less decision times. Our proposed technique is suitable for problems with a large number of classes due to its advantages of requiring less training time and computational complexity
An Integration of Project Management Body of Knowledge and Project Management Information System to Improve On-time Deliverable of Liquefied Natural Gas Station Construction Projects
Get PDFThe objective of this study is to improve the liquefied natural gas station construction project to achieve on-time delivery. Diverse tools and techniques are integrated to make various interrelated activities in the project occur effectively as planned with less cost, suggested by the Project Management Body of Knowledge (PMBOK) guideline and the Project Management Information System (PMIS). To implement the PMIS along with the PMBOK, the project management software and Internet of Things (IoT) are utilized for real-time long-distance monitoring and control of the project. The proposed approach is implemented at a real demonstration project. The results reveal that the proposed approach is quite effective, which help increase the number of projects completed on schedule from 75% in the last year to 100% this year. Moreover, the implementation of the PMIS also results in substantial reductions in the employment allowance for routine site inspections and the travel expense for round-trip vehicles travelling from the company to the site
Selection Model of Subcontractor Relationships by Using Discriminant Analysis
Get PDFSubcontractors usually handle some parts of special works in construction projects. The development of the subcontractor’s relationship is one of the main issues to ensure the project's success. Many existing models were proposed for evaluating the subcontractor prequalification and performance, but a selection model of subcontractor relationships was still neglected for supporting the decision-making of the main contractor. Currently, main contractors use only their experience and personal preference to choose the type of subcontractor relationships. These practices can reduce the opportunities for finding a suitable subcontractor who could add more value to future explorative work. Moreover, if they mismatch the relationship type with the subcontractor, the main contractors will work with a poor-performance subcontractor. Thus, this wrong selection has hindered the benefit of a long-term relationship subcontractor. This study developed a selection model of subcontractor relationships to solve the problem. The methodology of this research collected data from the primary contractor's assessment of 15 projects, with 93 subcontractors based on factors influencing the current relationship type. Then, the selection model of subcontractor relationships was developed by using discriminant analysis. As a result, time control in planning, work quality, cooperation, and trust factors that influenced the outcome of the model development, were able to classify subcontractors into short-term or long-term relationships. The finding result was also validated and shown at an acceptable level. Therefore, the model development could support the decision-making of the main contractor in choosing the type of subcontractor relationship
Prediction Sequence Patterns of Tourist from the Tourism Website by Hybrid Deep Learning Techniques
Get PDFTourism is an important industry that generates incomes and jobs in the country where this industry contributes considerably to GDP. Before traveling, tourists usually need to plan an itinerary listing a sequence of where to visit and what to do. To help plan, tourists usually gather information by reading blogs and boards where visitors who have previously traveled posted about traveling places and activities. Text from traveling posts can infer travel itinerary and sequences of places to visit and activities to experience. This research aims to analyze text postings using 21 deep learning techniques to learn sequential patterns of places and activities. The three main techniques are Convolutional Neural Network (CNN), Long Short-Term Memory (LSTM), Gated Recurrent Units (GRU) and a combination of these techniques including their adaptation with batch normalization. The output is sequential patterns for predicting places or activities that tourists are likely to go and plan to do. The results are evaluated using mean absolute error (MAE) and mean squared error (MSE) loss metrics. Moreover, the predicted sequences of places and activities are further assessed using a sequence alignment method called the Needleman–Wunsch algorithm (NW), which is a popular method to estimate sequence matching between two sequences
Study of Brake Pad Shim Modification to Improve Stability Against High Frequency Squeal Noise by Finite Element Analysis
Get PDFThis research studying on brake pad shim design with 4 configurations to improve the brake squeal noise phenomenon for high frequency noise in the range of 4-16 kHz. Various shims were designed with different configurations to increase structural damping and avoid instabilities in a brake system, which arise from friction drawing the vibration modes to coalesce between brake disc and brake pads. Then, the suspect brake module was tested in the laboratory using a dynamometer machine to confirm brake frequency noise parameters and conditions. The numerical models including brake disc, brake pad and brake pad shim were created using finite elements software and the unstable modes analysed for negative damping and positive real part values with the Complex Eigenvalue Analysis (CEA) technique. The simulation result showed that the instability of the brake system comes from mode coupling of the brake disc and brake pads in the out-of-plane modes (11ND) and (2 ND), respectively. The brake pads shim design1, design2 and design3 are component which goes in between the calipers and brake pads, were able to avoid high frequency brake squeal but make the noise move toward the direction of the lower frequency. The brake pad shim design4 is the good structure modification to avoid high frequency brake squeal and low frequency