Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Optimization of a Hybrid Carbon/Glass Composites Afterbody of the Amphibious Plane with Finite Element Analysis
Get PDFThe main objective of this research is to find the optimized lay up for theafterbody of the amphibious plane which can carried load according to ASTM F2245(Standard Specification for Design and Performance of a Light Sport Airplane).The finite element analyses of hybrid carbon/glass composites are carried out usingANSYS ACP under assumption that the hybrid carbon/glass fiber composites couldcombine the strong sides of carbon and glass fiber reinforced polymer to balance betweenstrength, weight and cost to achieve the requirement for each design of the aircraft.While the stress of the carbon and glass fiber in the structure are within the safety limit,the results show that the weight is minimum when the laminate ply pattern consists of 3.18mm foam core (D) sandwiched by 3 layers of carbon woven fabrics on both side[(±45)C(0/90)C(±45)CD̅]S. While the laminate ply pattern with 3.18 mm foam coresandwiched by 2 layers of carbon and 1 layer of glass woven fabric[(±45)C(0/90)C(±45)GD̅]S on both side have a good balance between weight and cost
Design and validation of flight dynamics system
Get PDFThis paper presents the architecture design of flight dynamics system (FDS) known as “EMERALD” developed by Geo-Informatics and Space Technology Development Agency (GISTDA) and Mahanakorn University of Technology (MUT). The capability of the system enables to provide the state vector of a satellite, mission analysis, orbit events and mission monitoring. The methodologies of orbit determination and event prediction modules implemented for mission management are presented and the validations of both are done by comparing with the previous FDS (Quartz) developed by EADS ASTRIUM. As a result of the implementation, the reduction of the operation time is significant and the prediction performance is high accurate and reliable when comparing with Quartz
Persistence of Nitrite-Oxidizing Bacteria in Entrapped Cell-Based Partial Nitrifying Reactor Treating Ammonia-Rich Wastewater
Get PDFA phosphorylated-polyvinyl alcohol (PPVA) entrapped cell-based reactor was employed to promote partial nitrification for ammonia-rich wastewater treatment. High partial nitrification (66% of nitrite accumulation in average) was achieved along the 165 days of operation indicating that the majority of nitrite-oxidizing bacteria (NOB) activity was suppressed probably as a result of low oxygen environment created within the PPVA gel matrix. However, some portion of nitrate (5-17.6% of the influent ammonia) always appeared in the reactor throughout the operation period. Next-generation sequencing and clone library techniques revealed that NOB with different substrate affinities including Nitrobacter, Nitrospira lineage I and II existed within the gel matrix. The finding speculates that substrate gradient-like microenvironment within the gel matrix probably serves the different physiological groups of NOB to maintain their cells and activities in the reactor. Therefore, instead of using low oxygen environment in gel matrix as a sole control strategy, an additional strategy like promoting free ammonia inhibition in reactor is also needed to affirm the stability of long-term partial nitrificatio
A Building Information Modeling (BIM)-Integrated System for Evaluating the Impact of Change Orders
Get PDFChange orders are inevitable in most construction projects. The conventional change order practice is usually associated with 2D drawings and various paper-based documents, which cannot illustrate the existing and altered building conditions efficiently. This often leads to misinterpretation and miscommunication among project participants. In addition, cost and schedule information, which is basic inputs for analyzing the impact of change orders, is usually scattered and poorly organized resulting in difficulties in retrieving it. The evaluation of cost and schedule impacts is often subjective and unsystematic contributing to construction disputes. Building information modeling (BIM) is widely used in modern construction projects. BIM is a promising construction information management tool, which can address the aforementioned challenges. In this paper, we develop the BIM-Integrated System for Evaluating the Impacts of Construction Change Orders (BIM-ISICO), which can systematically analyze three main impacts of a change order: physical conditions, schedule, and cost. The BIM-ISICO assists users in observing and visualizing the effect of a change order on building conditions systematically via 3D BIM models. The system can also evaluate the impacts of such change order on project cost and schedule. It establishes a new paradigm of delay and cost analysis by minimizing subjectivity and providing the auditing trails of change orders. To demonstrate its efficacy and practicality, the system is applied to an actual 18-story building project for analyzing the impact of a construction change order. The system can successfully assess and report all three aspects of change order impacts. These results can mitigate the conflicts between the project owner and the contractor about the construction claims resulting from change orders
Remotely-Controlled Low-Cost Digital Telescope
Get PDFThis paper presents a low-cost web controlled digital telescope which can benefit educational institutions. The system is composed of two webcams to acquire data. One is used as a wide field of view for localization purpose and the second one is used as a narrow field of view using a 40 cm focal length lens and an achromatic doublet to visualize celestial objects. The telescope orientation is performed remotely using two motors through Internet with an in-house developed soft- ware running on a Raspberry Pi 3 device. MQTT based server is used to provide a full wireless communication between the user and the telescope for orientation control, data visualization and acquisition. The telescope structure is built using a 3D-printer. An image processing algorithm is presented to calibrate mounting camera misalignment. The overlapping calibration is performed to localize the telescope image onto the large field-of-view image. It is based on Fourier domain cross-correlation technique
Dehydrogenation of Ethanol to Acetaldehyde over Co/C Catalysts
Get PDFThis study focuses on the production of acetaldehyde from ethanol by catalytic dehydrogenation using Co/C catalysts with different Co loading on the activated carbon derived from coffee ground residues. The simple impregnation was used to obtain the Co/C catalysts having Co loading of ca. 4 and 6 wt%. The catalysts were characterized using various techniques. The dehydrogenation of vaporized ethanol was conducted in order to measure the catalytic activity and product distribution at temperatures ranging from 250 to 400°C. Based on this study, it appeared that the Co/C catalyst having ca. 4 wt% of cobalt loading (4%Co/C) exhibited the highest ethanol conversion (54%) at 400oC with the acetaldehyde yield of 50%. In addition, all catalysts behaved similar catalytic properties, where the ethanol conversion increased with increasing the reaction temperature having acetaldehyde as a major product. The high activity obtained from 4%Co/C and C catalysts can be remarkably attributed to the high acidity to basicity (~1.50). Hence, the 4%Co/C is promising catalyst for ethanol dehydrogenation to acetaldehyde
The Effect of Water Evaporation in Automotive Windshield Defrosting
Get PDFWater evaporation during windshield defrosting is investigated paying particular attention to the effects of air humidity and wind speed. During the defrosting process, the ice layer on the windshield begins to melt as the temperature of the defrost air increases. Results have shown that the ice-turned-water can evaporate depending upon the ambient air humidity level and the wind speed. Water evaporation takes the heat otherwise available for melting, thereby delaying the ice melting process. It is found that at low wind speeds the effect of air humidity in delaying the ice-melting is minimal. However, at high wind speeds, (>10 m/s) water evaporation can take enough heat away from melting, thereby significantly reducing the ice removal rate. In relation to this, driver safety concerns associated with the reduction of ice melting rate are discussed
Synthesis of Light Hydrocarbons via Oxidative Coupling of Methane over Silica-supported Na2WO4-TiO2 Catalyst
Get PDFMethane is of great interest for conversion into high-value hydrocarbons (C2+) and olefins, via oxidative coupling of methane (OCM) using catalysts. In this work, Na2WO4-TiO2/SiO2 catalyst, along with the single catalysts of its components (Na2WO4/SiO2 and TiO2/SiO2), was investigated for OCM reaction to C2+. We found that 5 wt% Na2WO4+ 5 wt% TiO2 on the SiO2 support was a superior catalyst for OCM reaction compared to the single catalysts. The maximum C2+ formation of the Na2WO4-TiO2/SiO2 catalyst was found under test conditions of a N2/(4CH4:1O2) feed gas ratio of 1:1, a reactor temperature of 700 ºC, and gas hourly space velocity of 9,500 h−1, exhibiting 71.7% C2+ selectivity, 6.8% CH4 conversion, and 4.9% C2+ yield. Moreover, the activity of the catalyst had good stability over 24 h of on-stream testing. The characterizations of the Na2WO4-TiO2/SiO2 catalyst using XRD, FT-IR, XPS, FE-SEM, and TEM revealed that a crystalline structure of α-cristobalite of SiO2 was present along with TiO2 crystals, substantially enhancing the activity of the catalyst for OCM reaction to C2+
Hybrid Motor System for High Precision Position Control of a Heavy Load Plant
Get PDFThe lift up or press process with high precision position control is an important application in industries. An example of the process lift up and press is the process of a machine tool for drilling, milling, or injection. It is difficult to design the mechanism and controller to control the position of the base table accuracy because it needs to control the base position of the system with the weight varying in a large range. Also, the friction in the system would vary in a large range. This lead to low performance of the system in some range of load. Therefore, the new design system utilizes a DC motor and ball screw and pneumatic actuator to create the hybrid motor system for applying to the lift up and press system. The pneumatic actuator is designed to support the heavy load and the DC motor and ball screw is designed to control the position. Then, the developed hybrid motor can be used to improve the performance of the system. The simulation and experiment results show that the developed system can improve the rise time, setting time, and steady state error. Then, the time response of the system with heavy load look similar to the time response of the system with light load. Moreover, the developed hybrid motor technique can apply to the applications such as to control the 3D powder painter tank base position, and the silicon injection system, the 3D print head, which is a challenge system due to the high friction in tube
Seismic Shear Strengthening of Reinforced Concrete Short Columns Using Ferrocement with Expanded Metal
Get PDFTypical reinforced concrete short column is brittle in shear rather than flexure under lateral cyclic loading due to its shear deficiency. This paper presents the improvement of seismic behaviour of the reinforced concrete short columns which were strengthened by using ferrocement with expanded metal. Full scale experiments were conducted for two strengthened concrete columns with different volume fractions of expanded metal and the control specimen under lateral cyclic loading. It was found that the seismic behaviour in terms of the shear strength, stiffness, displacement ductility, and energy dissipation were significantly improved. The expanded metal mesh with the high specific surface provided the better performance for controlling the crack propagation. The brittle shear failure mode of the stirrup was reduced and the ductile flexure mode of the longitudinal reinforcement was dominant. The reduced shear force of the stirrup was compensated by the shear force of the expanded metal reinforcement which experienced relatively large strain. The technique of steel angle installation at the corners of column can successfully prevent the effect of sharpened corner wrapping of the mesh. A model to predict the shear strength of the strengthened column is presented in term of the global efficiency factor for expanded mental.