Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Problems Causing Delays and Risk Factors in Welding Construction Projects of Thailand
Get PDFWelding delays are one of the major risks in steel construction industry in Thailand. Therefore, it is essential to study and analyze the risk factors that lead to problems causing welding construction delays. This studied focused on delay risk factors in causes of construction projects collected from literature review having the different construction processes, project period, culture, countries, and amount of delay factors for contribution in welding construction projects. Questionnaire surveys and interviews were conducted on major companies connected to welding works in support of the construction projects in Thailand to survey thought problems causing delays and risk factors. Risk factors related to internal and external risk were rated among the risks identified problems. Issues such as material receiving, performance, qualified and language barriers were also highlighted in the questionnaire and during interviews. Notably, the problem such as “multilingual and multicultural” caused ineffective communication. A case study used the FMEA technique to analyze the severity, occurrences and detection, and evaluate to risk priority number. Significant risks were analyzed and compared between the Modified RPN and WRPN method for finding the “Critical risk”. The new finding can contribute additional help for project managers to predict and mitigate welding construction project delays
Potassium Carbonate Supported on gamma-Alumina Sorbent Regeneration in Fluidized Bed Reactor for Carbon Dioxide Capture Technology
Get PDFNowadays, the world is facing severe climate change due to the rapid increase in the world population and the continuing growth of the economy and industry. These lead to substantial greenhouse gas emissions into the atmosphere, especially carbon dioxide, which causes global warming. Thus, carbon dioxide (CO2) capture becomes an essential technology for mitigating adverse effects on the atmosphere. The solid sorbent is an appropriate alternative for CO2 capture because it is cheap, environmentally benign, and recyclable. In this study, solid-sorbent regeneration using potassium carbonate supported on gamma-alumina in a fluidized bed reactor was investigated. The effects of operating variables of solid sorbent regeneration were studied by varying the temperatures of 100, 200, and 300 degrees Celsius and pressures in the range from 0 to 1 atmospheric pressure. The results showed that regeneration temperature had a positive effect and initial pressure had a negative effect on the sorbent regeneration, respectively. The sorbent regeneration can be enhanced by increasing the regeneration temperature and decreasing the initial pressure. The optimal condition for sorbent regeneration was at the temperature of 300 degrees Celsius and initial pressures of 0.35 bar. Kinetic studies of the sorbent regeneration were also conducted, and obtained a pseudo-second-order model to be the best-fit model
Effects of Reactor Loading and Solvent Addition on Catalyst-Free Glycerolysis of Palm Oil
Get PDFGlycerol is a by-product of biodiesel production. Every three moles of biodiesel produced, glycerol is released in one mole, which is around 10 wt.% of the total products. The crude glycerol from supercritical transesterification has a higher purity than that from alkaline transesterification. Monoglyceride is an anionic surfactant widely used in many applications. In this work, the glycerolysis reaction of palm oil and glycerol was studied using isopropanol as the solvent. The investigated important parameters in this study were reaction time in range of 30-150 minutes, reactor loading in range of 40-80 %, and molar ratio of isopropanol to glycerol to palm oil in range of 0-30. The glycerol to palm oil molar ratio was constant at 5 to 1. The results showed that parameters affected conversions and yields were reactor loading and solvent addition. The highest monoglyceride yield, 37.4%, was obtained at 260 ˚C in 150 minutes and 40 % of reactor loading. Molar ratio of glycerol to palm oil to isopropanol is 5:1:15. A central composite design (CCD) of 48 experiments investigated the effects on monoglyceride content (%MG) of temperature (220 to 260 ˚C), reaction duration (30 to 150 min), and molar ratio of IPA to palm oil (0:1 to 30:1). The %MG was substantially and statistically significantly enhanced (p < 0.0001) at higher temperatures and longer reaction duration. An analysis of variance confirmed that the molar ratio of IPA to palm oil had a much less significant effect (p = 0.0255) on %MG. The crude glycerol obtained from a biodiesel production plant was compared with pure glycerol at the optimal condition. A %MG of 46.58% was observed using crude glycerol as reactant because of the yield-limiting effects of water in crude glycerol
The Design of Bunch Shaker and the Date Fruit Detachment Force
Get PDFIn this work, the design and construction of a tractor-mounted shaker used for the removal of date fruits from the bunch is presented. The dynamic force developed by this shaker is calculated and the tensile force required to detach the date fruit at subsequent stages of fruit maturity is measured with the prospect of relating the two forces. Such a relation would facilitate the design of shaker stroke and frequency which would develop a dynamic force equivalent to the detachment force requirement for any type of date variety. The experimental results confirmed that the detachment force decreased significantly with the progress of fruit maturity. The average tensile detachment force at the final stage of fruit maturity was 6.8 N which is 20% of the average tensile detachment force at the first stage of fruit maturity (33.4 N). However, the dynamic force developed by the bunch shaker at different shaking frequencies, which ranged from 0.42 N to 2.68 N, is much lower than the tensile detachment force. This implies that dates removal from the bunch by a bunch shaker cannot be attributed to the development of a dynamic force which exceeds the tensile detachment force requirement. Consequently, the tensile fruit detachment force cannot be utilized as a criterion for the design of a date bunch shaker
Life Cycle Carbon Dioxide Emissions Assessment in the Design Phase: A Case of a Green Building in Vietnam
Get PDFBuildings are responsible for about 30% of the total CO2 emissions globally. To reduce this amount of CO2, developing green buildings is one of the best approaches. However, this approach is undeveloped in Vietnam due to lacking methods to evaluate design alternatives to meet the criteria of green buildings. This paper presents a life-cycle CO2 analysis (LCCO2A) as a tool to support the decision-making process in the design phase of a 75-year-lifespan green building in Vietnam. The study conducts LCCO2A for two design alternatives (with different bricks usage and glass types) and points out the reasons for the differences. Comparing the first alternative with the second one, the results show slight variations in the amount of CO2 emissions in the erection and demolition phases (with an increase of 21.81 tons and a reduction of 106.1 tons of CO2eq, respectively), and a significant difference in the operation phase (10,631.52 tons of CO2eq or 58.34% reduction). For the whole life-cycle, the second design scenario, which uses “greener” materials shows a great decrease of 10,715.81 tons of CO2eq or 37.54%. By comparing its results with the findings in the literature, this research proves the environmental dominance of green buildings over other building categories
A Case Study of BIM Application in a Public Construction Project Management Unit in Vietnam: Lessons Learned and Organizational Changes
Get PDFPublic construction projects in Vietnam are managed by project management units (PMUs). A PMU should consist of the board of directors, a project office, functional and project executive departments. Functional departments are in charge of investor’s responsibilities, while project executive departments are in charge of project execution. This paper discusses the practice of BIM adoption in a case study of a PMU (SPMB) in a public project. Lessons learned include the fact that, while BIM could provide certain benefits to the project, it also extended the project's duration and increased project costs. The SPMB, previously departmentalized by project phases, has changed its organizational structure by establishing a task group made up of professionals from various project executive departments, leading directly by the SPMB leaders, to address BIM issues, though only some basic uses of BIM have been applied. The functions of the project executive departments have also been adjusted due to the application of a new procurement form and the emergence of new processes, and the requirements for a new type of capability (BIM). Subsequently, other elements of the organizational design have been changed accordingly. The lessons learned contribute to the current understanding that PMUs need substantially organizational restructuring for BIM implementation effectively and efficiently while also well-prepared for negative impacts
The Dynamics of Commingled Production
Get PDFCommingled production strategies have been applied successfully worldwide because of the advantages they provide in terms of cost effectiveness and completion simplicity. However, a commingled production approach raises several challenges for reservoir management. The behavior of a commingled well is much more complicated than that of a single-layer well. However, there is little knowledge or experience sharing documented in the literature. The objectives of this study are to comprehensively review reservoir engineering knowledge and performance of commingled wells, and to propose tools for reservoir management decisions. This study summarizes the current knowledge of decline curve analysis (DCA) and material balance equations (MBE) for commingled production available in the literature, and reviews lessons learned from production logging and water shut-off lookback studies in Gulf of Thailand operations. Based on this information, this study proposes the use of a “risky-sand matrix”, of perforation best practices, and of commingled well models. Through these approaches, petroleum and reservoir engineers will be better able to understand the performance characteristics of commingled wells and will be in a position to make better reservoir management decisions
Flight Delay Prediction Using a Hybrid Deep Learning Method
Get PDFThe operational effectiveness of airports and airlines greatly relies on punctuality. Many conventional machine learning and deep learning algorithms are applied in the analysis of air traffic data. However, the hybrid deep learning (HDL) model demonstrates great success with superior results in many complex problems, e.g. image classification and behaviour detection based on video data. Interestingly, no previous attempts have been made to apply the concept of HDL in analysing structured air traffic data before. Hence, this research investigates the effectiveness of the HDL in the departure delays severity prediction (i.e. on-time, delay and extremely delay) for 10 major airports in the U.S. that experience high ground and air congestion. The proposed HDL model is a combination of a feed-forward artificial neural network model with three hidden layers and a conventional gradient boosted tree model (XGBoost). Utilising the passenger flight on-time performance data from the U.S. Department of Transportation, the proposed HDL model achieves a sharp rise of 22.95% in accuracy when compared to a pure neural network model. However, with current data used in this research, a pure machine learning model achieves the best prediction accuracy
A Review of Supercritical Technologies for Lipid-Based Biofuels Production: The Glycerol-free Processes
Get PDFSupercritical transesterification of lipid-based biomasses, a recent technique to produce biofuel without a catalyst, is discussed. This review focused on a glycerol-free process. The supercritical reactants include dimethyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate (ETA), and methyl tert-butyl ether. The by-products from the glycerol-free process can improve both the quantity and quality of the resultant biofuel. This review suggests that supercritical transesterification of lipid-based biomasses using ETA as a co-reactant can provide the most valuable advantages, as involves inexpensive and renewable resources, which are important for biofuel production and sustainability
Pretreatment of Palm Fruit by Using a Conveyor Belt Microwave Prototype
Get PDFThis paper presents a microwave drying prototype, which is a conveyor belt design for oil palm pretreatment. The prototype consists of four 800 W magnetrons launching electromagnetic energy to the rectangular waveguide cavity. Palm fruit was fed in the cavity by the conveyor belt and pretreated in the cavity. The cavity size was designed optimally to ensure that temperature distribution in the palm fruit is uniform. Another conveyor belt is applied to the cavity output to feed out the pretreated fruit. Two corrugated waveguide filters were installed at the conveyor belt ends to suppress the microwave leakage. Three hundred sixty palm fruit were pretreated to prove the prototype concept. From the experiment results, the prototype heated palm fruit to the temperature required for inhibiting lipase enzyme within 120 seconds. It is found that free fatty acids in the treated palm fruit was well below 2% even 1 week storage