Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Weekly Forecasting Model for Dengue Hemorrhagic Fever Outbreak in Thailand
Get PDFA dengue virus causes diseases, including dengue hemorrhagic fever (DHF) which induces several sicknesses and deaths in Thailand. DHF is categorized as one of the most dangerous communicable diseases by the Ministry of Public Health Thailand (MoPH); moreover, the MoPH also sets strict protocols and encourages forecasting techniques for monitoring and dealing with the outbreaks. This research aims to utilize the data that were gathered from external sources, e.g. Google Trends data and meteorology data, to forecast the number of cases that will occur within the 7 day-interval in the next 1–4 weeks. Six provinces—including Chiang Rai, Mukdahan, Pattani, Phichit, Ayutthaya, and Ratchaburi—were selected as they represent the unique patterns of dengue outbreaks in Thailand. The machine learning models—including Random Forest, AdaBoost, Extra-Trees, and Regularized Regressions—were used to forecast the number of the cases. The performances of these models were compared to the performances of the traditional time series model including Naïve model and Moving Average. The proposed machine learning models for Chiang Rai, Mukdahan, and Pattani yield better results than those of the traditional models
A BIM-Integrated Relational Database Management System for Evaluating Building Life-Cycle Costs
Get PDFSustainable procurement is an important policy for mitigating environmental impacts attributing to construction projects. Life-cycle cost analysis (LCCA), which is an essential requirement in sustainable procurement, is a principal tool for evaluating the economic efficiency for the total life-cycle budget of a building project. LCCA is a complex and time-consuming process due to repetitive complicated calculations, which are based on various legal and regulatory requirements. It also requires a large amount of data from different sources throughout the project life cycle. For conventional data management systems, data are usually stored in the form of papers and are input into the systems manually. This results in data loss and inconsistent data, which subsequently contribute to inaccurate life-cycle costs (LCCs). Building information modeling (BIM) is a modern technology, which can potentially overcome the asperities of the conventional building LCCA. However, existing BIM tools cannot carry out building LCCA due to their limited capabilities. The relational database management system (RDBMS) can be integrated with BIM for organizing, storing, and exchanging LCCA data in a logical and systematic manner. In this paper, a BIM-integrated RDBMS is developed for compiling and organizing the required data and information from BIM models to compute building LCCs. The system integrates the BIM authoring program, the database management system, the spreadsheet system, and the visual programming interface. It is part of the BIM-database-integrated system for building LCCA using a multi-parametric model. It represents a new automated methodology for performing building LCCA, which can facilitate the implementation of sustainable procurement in building projects
Effective Crew Allocation Using Discrete-Event Simulation: Building Scaffolding Case Study in Thailand
Get PDFA paradigm was developed to illustrate the performance and capabilities of discrete-event simulation (DES) in dealing with the complexity and uncertainty of construction processes. EZStrobe (a promising DES tool) was utilized due to its simplicity and the moderate effort required. A case study investigated the scaffolding installation process for a high-rise building project in Thailand. The activity cycle diagrams (ACDs) were constructed accordingly to represent the complex construction processes and associated activities of the case study. Data analyses were performed to propose an effective strategy that contributed substantially to productivity improvement. The results showed that for five workers, the ratio of installers to delivery workers to lower-level workers of 1:1:3 produced the lowest total idle time. Nevertheless, doubling the numbers of workers produced the shortest total construction duration but with higher idle time and construction labor cost. The crew fleet was effectively allocated depending on two main attributes: (1) proportion between installers and delivery workers; and (2) number of lower-level workers. The findings from this study can further direct project planners to achieve proficient onsite resource arrangements, especially under time and cost constraints
Pyrolysis Kinetic Analysis of Biomasses: Sugarcane Residue, Corn Cob, Napier Grass and their Mixture
Get PDFThe aim of this study is to investigate pyrolysis kinetic parameters of three high potential energy biomasses including sugarcane residue (tops and leaves), corn cob and Napier grass via thermogravimetry analysis (TGA). In addition, those of their mixture at 1:1:1 by mass is explored. Activation energy and pre-exponential factor were the two considered parameters calculated by following the Ozawa-Flynn-Wall method using condition of 30-900°C with heating rates of 5, 10, 20 and 40°C/min. The derivative thermogravimetric (DTG) curves indicated that there might be at least three different component structures in corn cob. The effective values of the both parameters were almost similar as 214.54, 216.60, 212.51 kJ/mol and 1.510E+19, 1.575E+19, 1.562E+19 min-1 for the sugarcane residue, the corn cob, the Napier grass, respectively. Finally, the ternary diagram suggested that the increase of Napier grass proportion would slightly affect the conversion of pyrolysis by reducing the total activation energy of the biomass mixture
A Nonlinear Model for Online Identifying a High-Speed Bidirectional DC Motor
Get PDFThe modeling system is a process to define the real physical system mathematically, and the input/output data are responsible for configuring the relation between them as a mathematical model. Most ofthe actual systems have nonlinear performance, and this nonlinear behavior is the inherent feature for thosesystems; Mechatronic systems are not an exception. Transforming the electrical energy to mechanical one orvice versa has not been done entirely. There are usually losses as heat, or due to reverse mechanical, electrical,or magnetic energy, takes irregular shapes, and they are concerned as the significant resource of that nonlinearbehavior. The article introduces a nonlinear online Identification of a high-speed bidirectional DC motor withdead zone and Coulomb friction effect, which represent a primary nonlinear source, as well as viscosity forces.The Wiener block-oriented nonlinear system with neural networks are implemented to identify the nonlin-ear dynamic, mechatronic system. Online identification is adopted using the recursive weighted least squares(RWLS) method, which depends on the current and (to some extent) previous data. The identification fitnessis found for various configurations with different polynomial orders, and the best model fitness is obtainedabout 98% according to normalized root mean square criterion for a third order polynomial
A Parametric Investigation of the Steam Injection Gas Turbine System on a Cogeneration Plant
Get PDFThe aim of this study is to conduct a parametric investigation of the steam injection gas turbine system by focusing on the effect of the steam mass flow rate on the energy transfer behaviors of a cogeneration plant. A thermodynamic model of two gas turbine cycles and one steam turbine cycle and a heat transfer model of the heat recovery steam generator are developed. A successive iteration is employed to solve a set of equations and obtain a converged solution. The result shows that by increasing the mass flow rate for the steam injection gas turbine system from 0 to 2 kg/s, the input energy rate from the fuel and the total electrical output power from the cogeneration plant are increased, resulting in an increase of the cogeneration electrical efficiency from 49.9% to 50.4%. On the other hand, the output heat rate from the steam from the cogeneration plant is decreased, resulting in a decrease of the cogeneration heat efficiency from 8.5% to 5.4%. Consequently, the primary energy saving of the cogeneration plant decreases from 16.6% to 14.9%. 
Weldability of Aluminum-Steel Joints Using Continuous Drive Friction Welding Process, Without the Presence of Intermetallic Compounds
Get PDFWeldability of aluminum-steel joints has been studied mainly to avoid the formation of IMC. Nowadays, there are two ways to control the effect of FexAly in welding: 1) the elimination of IMCs or 2) the generation of a thin and homogeneous layer of these phases. In this way, the present work explores the first route, manufacturing joints aluminum-steel using solid state welding process. In order to evaluate the effect of the welding parameters, temperature measures were carried out during the process as well as the microstructural evaluation using optical microscopy and SEM. Finally, the welded joints were subject to tensile strength tests to evaluate their mechanical behavior and try to stablish the nature of the interfacial bonding between both metals. The microstructural characterization of the joints does not reveal the formation of IMCs; this is attributed to the low temperature reached during the process, lower than 545 °C. The welded joint failures in the TMAZ, in the low hardness zone, product of the over aging of the precipitates β”. The nature of the bonding in the interface is not clear yet, but it is considered that the atomic diffusion trough the interface favors the joint formatio
Making Undergraduate Labs Challenging and Useful
Get PDFLearning through laboratory work is critical in high quality science education. Traditional engineering labs are useful but not challenging. However, when the same labs are repeated every year, and students know the results, it is questionable how much is really learned. Students may copy the results from last year’s labs, making it difficult for instructors to evaluate their work. To address this problem, the Mechanical Engineering Experimentation and Laboratory II class was revised. A new lab designed to be challenging and useful by using a current research topic to guide it. The class taught in new class environment with state-of-the-art facilities. Students learn instrumentation in a way that forces them to think about the problem, develop a method to measure a phenomenon, and draw conclusions about the results. The tangible connection to research motivates students. It takes professors more time to create these labs. However, since the results fold directly into their research objectives, i.e., gathering data needed for publications, the approach ultimately becomes an efficient use of time. It is fairly common for professors to ignore undergraduate labs, but this paper shows that with a little bit of effort, these labs can provide a significant learning experience for students. Based on the survey, more than 90% of students agree that the new lab help them to develop defining problem, designing experiment, analyzing, concluding, and reporting skills. More than 70% of students agree that they learn new measurement equipment for the new lab. Also, 91% of students would recommend other students to take the new lab. Moreover, this paper shows that the results from the lab lead to the manuscript which has submitted to a journal. 
Using Artificial Neural Network for Selecting Type of Subcontractor Relationships in Construction Project
Get PDFSince some subcontractors could perform their professional skills faster and less expensive, many main contractors have adapted those companies to help their construction works and gained more profits. After the relationship between main contractor and subcontractor was consistently developed by many construction projects, main contractors would be willing to define a potential subcontractor who could ensure a good productivity in the future. Previously, main contractors were experienced by wrong selection of subcontractor in relationship development. Thus, it could cause some controversies between main contractor and subcontractor and hinder benefits with a right subcontractor for a long run business. To minimize the problem of main contractor, this paper used an artificial neural network as a tool for determining the subcontractor in relationship development. As the result, the artificial neural network provided higher accuracy in training and validating data and it could give main contractor more confident in decision making for selecting type of subcontractor relationships
Waste Collection Vehicle Routing Problem Model with Multiple Trips, Time Windows, Split Delivery, Heterogeneous Fleet and Intermediate Facility
Get PDFWaste Collection Vehicle Routing Problem (WCVRP) is one of the developments of a Vehicle Routing Problem, which can solve the route determination of transporting waste. This study aims to develop a model from WCVRP by adding characteristics such as split delivery, multiple trips, time windows, heterogeneous fleet, and intermediate facilities alongside an objective function to minimize costs and travel distance. Our model determines the route for transporting waste especially in Cakung District, East Jakarta. The additional characteristics are obtained by analyzing the characteristics of waste transportation in the area. The models are tested using dummy data to analyze the required computational time and route suitability. The models contribute to determining the route of transporting waste afterward. The WCVRP model has been successfully developed, conducted the numerical testing, and implemented with the actual characteristics such as split delivery, multiple trips, time windows, heterogeneous fleets, and intermediate facilities. The output has reached the global optimal for both dummy and real data