Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
Not a member yet
1223 research outputs found
Sort by
Biofuels Produced by Fischer-Tropsch Synthesis over Silica-supported Iron-Based Catalysts Prepared by Autocombustion Method
Get PDFThe purpose of this study was to evaluate the effect of different silica types on iron (Fe)-based catalysts containing copper and potassium prepared by autocombustion for direct use in Fischer-Tropsch Synthesis (FTS) without a reduction step. The catalysts were characterized through nitrogen (N2) adsorption, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The FTS performance of each catalyst was evaluated in a fixed-bed reactor at 300 ◦C, 1.0 MPa, a catalyst weight to volume flow rate of 10 gcat h/mol and a hydrogen (H2)/carbon monoxide (CO) molar ratio of 1. The pore size of the silica had an important influence on the formation of the Fe active phases and subsequent FTS activity. The presence of iron carbide (FexC), which is known to be one of the active Fe phases, was demonstrated by the XRD and TEM analyses. Larger crystallite sizes in the large pores were much easier to accommodate FexC than the smaller crystallite sizes in the small pores. The Fe-based catalysts supported on the silica with the largest pores gave the highest CO conversion level at 86.5%, with a 28.1% C2–4 selectivity and 17.3% C5+ selectivity under these operating conditions. Interestingly, this is an alternative approach to synthesize nanostructured metallic catalysts on silica and to produce clean biofuel for the fuel industry and transportation
Effect of Temperature for Platinum/Carbon Electrocatalyst Preparation on Hydrogen Evolution Reaction
Get PDFThis research was carried out to study the effect of preparation temperature of the Pt/C electrocatalyst on the hydrogen evolution reaction (HER). Pt/C electrocatalyst was synthesized using the polyol method in ethylene glycol with 1 M ascorbic acid as a mild reducing agent. The investigated parameter was the temperature, which will vary from room temperature to 120˚C. From the cyclic voltammetry (CV), the results showed that the Pt/C electrocatalyst synthesized by the polyol method at room temperature and 60˚C cannot promote hydrogen desorption peak compared to other catalysts. The Pt/C catalyst synthesized at 100˚C gave the highest electrochemical surface area (ESA) at around 32.59 m2/gPt. From the linear sweep voltammetry (LSV) tested in an acid solution, the Pt/C catalyst synthesized at 100˚C exhibited the highest HER activity. The exchange current density, Tafel slope and overpotential at 10 mA/cm2 were around 5.208 mA/cm2, -59.3 mV/dec and -0.277 VSCE, respectively. From the value of Tafel slope: -59.3 mV/dec, it indicated that the mechanism of the 20%Pt/C electrocatalyst synthesized at 100˚C catalyst occurs through Heyrovsky mechanism
Influence of Associated Cations on Chloride Ingress into Concrete Structures
Get PDFThis article presents an experimental study on the effect of different types of chloride-based deicing salts on the rate of chloride penetration into concrete structures. Three different types of deicers commonly used for deicing and anti-icing operations, NaCl, CaCl2, and MgCl2, were selected to investigate the influence of associated cations on the rate of chloride ingress into concrete. The concentration profiles of various ions were measured including Cl-, Na+, K+, Mg2+ and the effect of different cations on the diffusion rate of chloride ion into concrete was systematically studied. The test data were compared to numerical results obtained from a numerical model developed based on the Nernst-Planck equation which considered the ionic coupling effects among ions in chloride solutions and ions in concrete pore solution, Na+, K+, OH-. The test results illustrated that cations in different chloride solutions have significant effects on the penetration rate of chloride ions. This can be summarized in the order of CaCl2 > NaCl > MgCl2 from the fastest to slowest chloride ion penetration. In the case of various salt combinations tested, the diffusion rate of chloride ions can be ranked as NaCl + CaCl2 > CaCl2 + MgCl2 > NaCl + MgCl2. The total chloride concentration obtained from experimental results were compared to the numerical model and a good agreement was observed
A Fuzzy Credibility-Based Chance-Constrained Optimization Model for Multiple-Objective Aggregate Production Planning in a Supply Chain under an Uncertain Environment
Get PDFIn this study, a Multiple-Objective Aggregate Production Planning (MOAPP) problem in a supply chain under an uncertain environment is developed. The proposed model considers simultaneously four different conflicting objective functions. To solve the proposed Fuzzy Multiple-Objective Mixed Integer Linear Programming (FMOMILP) model, a hybrid approach has been developed by combining Fuzzy Credibility-based Chance-constrained Programming (FCCP) and Fuzzy Multiple-Objective Programming (FMOP). The FCCP can provide a credibility measure that indicates how much confidence the decision-makers may have in the obtained optimal solutions. In addition, the FMOP, which integrates an aggregation function and a weight-consistent constraint, is capable of handling many issues in making decisions under multiple objectives. The consistency of the ranking of objective’s important weight and satisfaction level is ensured by the weight-consistent constraint. Various compromised solutions, including balanced and unbalanced ones, can be found by using the aggregation function. This methodology offers the decision makers different alternatives to evaluate against conflicting objectives. A case experiment is then given to demonstrate the validity and effectiveness of the proposed formulation model and solution approach. The obtained outcomes can assist to satisfy the decision-makers’ aspiration, as well as provide more alternative strategy selections based on their preferences
Sustainable Development of Elevated Shell Platform
Get PDFShell structure has a unique thin, curved plate shaped yet strong enough to transmit applied forces by compressions but only being constructed as a roof structure with minor external load applied onto it. The objectives of this research are to study the feasibility in proposing elevated shell platforms in resisting heavy loading, to investigate the effect of shell geometric on elevated shell platforms and to identify the suitable shell geometric as economic and sustainable in construction development. Five different geometries of shell structure have been proposed which are dome, cone, pendentive, clam shape and leaf-like shape. LUSAS software has been used to analyze the different geometries of the shell and study the effect of stresses and deformation. The optimum height was determined by convergence test and proceeded to the modelling phase to obtain the output of stresses. In findings, this study has justified that the elevated shell platform is feasible to be applied in sustainable industry development and the effect of each different geometric has been identified by stress comparison. Most suitable geometric which is toroidal has been determined by extracting the least value of maximum stresses produced, with the optimum surface area provided to accommodate the maximum load applied
Perception of Lecturers and Students Regarding the Illuminance in the Lecture Theatres and Tutorial Rooms: Case Study in Universiti Tunku Abdul Rahman (UTAR)
Get PDFEven though artificial lighting is widely used nowadays, it has several negative impacts on human health. Therefore, this paper reported research that comparing the illuminance level in the learning environment in UTAR and recognizing the users’ insights on the illuminance level. Lux meter and questionnaires were used for data collection. Questionnaires were administered to 312 respondents. The results show that the illuminance level in some of the tutorial rooms is too bright and left on even when the rooms are empty. From the descriptive analysis, it is found that almost all the respondents are satisfied with the illuminance level in both research venues. Based on the t-test, it is found the significance for pair 1 and pair 2 is greater than 0.05. Hence, there is no similarity between both research venues. Pair 1 is about the lighting condition preferred by the respondents, while pair 2 is about the condition in both research venues which includes the existence of glaring vision, headache, eye tiredness, and conditions that affect student performance. This paper concludes by suggesting that individual switches be provided for each of the bulbs
Support Vector Machine for Regression of Ultimate Strength of Trusses: A Comparative Study
Get PDFThanks to the rapid development of computer science, direct analyses have been increasingly used in the design of structures in lieu of member-based design methods using the effective length factor. In a direct analysis, the ultimate strength of a whole structure can be sufficiently estimated, so that the need for member capacity checks is eliminated. However, in complicated structural design problems where many structural analyses are required, the use of direct analyses requires an excessive computation cost. In such cases, Machine Learning (ML) algorithms are used to build metamodels that can predict the structural responses without performing costly structural analysis. In this paper, the support vector machine (SVM) algorithm is employed for the first time to develop a metamodel for predicting the ultimate strength of trusses using direct analysis. Several kernel functions for the SVM model, including linear, sigmoid, polynomial, radial basis function (RBF), are considered. A planar 39-bar nonlinear inelastic steel truss is taken to study the performance of the kernel functions. The results confirm the applicability of the SVM-based metamodel for predicting the ultimate strength of trusses. In particular, the RBF appears to be the best kernel among others. This investigation also provides a deeper understanding of the effect of the parameters on the efficiency of the kernel functions
Practical Method to Evaluate the Effects of the Sensor and the Environment on the Measurement of Lightning-Generated Electric Field Signatures
Get PDFIndirect lightning measurement, using sensors and remote systems that record the radiated electric fields, is one of the most used methods to study and characterize this type of electrical discharges. This is due to its simplicity of implementation, low cost and the valuable information it provides. However, the measurement of the lightning-generated electric fields (LEF) can be influenced by factors such as the type of sensor, its physical features and its location, as well as by characteristics of the electromagnetic environment like geographical features, the structures that surround the measurement station and the materials of these objects. Under this consideration, this paper proposes a generalized method focused on the identification of those parameters that affect significantly influence the LEF measurement, as well as the process to estimate the correction factor of any measuring system designed for this purpose. This factor is important, as it indicates the proportion in which the signals of interest are attenuated or amplified. The method includes a review about the characteristics of the sensors, their connection scheme and a detailed analysis of the effect of the surrounding structures, taking into account parameters such as the permittivity and electrical conductivity of the materials. Finally, with the aim of presenting quantitative results, the proposed method is validated using as a practical case the information from the LEF automated measuring station owned by the Universidad Distrital Francisco José de Caldas, located in Bogotá, Colombia
Analyzing Productivity and Behavior of Plastic Drop-Off Points: A Case Study of Send Plastic Home Project in Plastic Waste Recycling during COVID-19 Outbreak
Get PDFIn this work, the Productivity Index (PI) was developed for evaluating ten plastic drop-off points along the Sukhumvit Road, Bangkok, Thailand. Factor Analysis of Mixed Data (FAMD) was employed to study the effects of various parameters on drop-off point’s performance. To explore plastic separation behaviors, the structured questionnaires were created based on the extended Theory of Planned Behavior, and the questionnaire’s responses were then analyzed through the Structural Equation Model (SEM). The highest PI (0.0058) was observed from a drop-off point located in the shopping mall while that installed in a restaurant exhibited the lowest PI (0.0008). Besides environmental attitude and perceived behavioral control, a drop-off point facility was proved as another factor influencing people’s intention towards plastic waste separation behavior. To improve the PI, drop-off point’s bin design and location should be carefully optimized. Moreover, public relation on drop-off point campaigns and knowledge on household plastic waste separation should be promoted. These findings are helpful for the improvement or expansion of plastic drop-off point facilities as well as for the future development of waste recycling policy
Properties of Barium Ferrite Nanoparticles and Bacterial Cellulose-Barium Ferrite Nanocomposites Synthesized by a Hydrothermal Method
Get PDFBarium ferrite (BFO) is a class of hard magnetic materials which is technologically important for many applications. Likewise, bacterial cellulose (BC) is a natural cellulose with a unique nanostructure and properties. Particularly, magnetic BC membrane, produced by incorporation of magnetic nanoparticles (NPs) in the BC structure, has recently been a research focus of many research groups. In this work, BFO NPs and BC/BFO nanocomposites were fabricated by hydrothermal synthesis. The BFO NPs could be fabricated only when the synthesis temperature reached 290 °C, with the faceted plate-like shape. Increasing the synthesis temperature gradually changed the magnetic properties from paramagnetic to superparamagnetic and ferromagnetic. Maximum Ms, Mr and Hc of 43 emu/g, 21 emu/g, and 1.6 kOe, respectively, were found. For BC/BFO nanocomposites, the hydrothermal synthesis conditions were limited by the stability of BC, i.e., 150 – 210 °C (for 1 h), or 1 – 7 h (at 190 °C). Using the higher temperature or time resulted in disintegration or decomposition of BC. It was found that very small NPs were coated on the BC nanofibers but the BFO phase was not observed by XRD. However, the magnetic measurement showed the hysteresis loops for the nanocomposites synthesized at 190 °C for 3 – 7 h. The observation of the hysteresis loops could be attributed to a small fraction of BFO in the nanocomposite that cannot be detected by XRD. The BC/BFO nanocomposite membranes were demonstrated for their magnetic attraction, flexibility, and lightness, which make them potential uses for flexible information storage or lightweight magnets