Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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The Strategy of Visual Inspection for Non-Geometric Parts by using Screen Display Techniques
Get PDFThe objective of this research is to determine the effectiveness of visual inspection strategies with different screen display techniques for non-geometric parts in terms of inspector performance measures to identify an effective strategy for inspecting non-geometric parts. The study is divided into three experimental phases. Phase I and Phase II compare the effectiveness of defect search patterns and training patterns respectively, to determine the best effective patterns. The results of both studies were integrated into screen display techniques to determine the most effective visual inspection strategy by using a visual inspection program in the final phase. Phase III compares the effectiveness of visual inspection with the strategy of screen display technique application. The evaluation of the effectiveness of all phases in regard to the performance of participants was indicated by speed and accuracy of the visual inspection. The results of the studies found that the visual inspection strategy with a hybrid screen display technique was the best strategy for visual inspection. This strategy will make visual inspection performance 13.40 sec faster per piece and increase accuracy by 50.83%. The application of the visual inspection strategy can be a strategy for practice before performing actual inspections and can have applications for other inspection work, especially for defect inspection of non-geometric shapes and complex shapes
Analysis of Failing load and Optimization of Hot Air Welding Parameters on PVC-Acrylic Coated Polyester Fabric by Taguchi and ANOVA Technique
Get PDFThere are several factors affecting the strength of welding seam through hot air for PVC-acrylic coated polyester fabrics. To obtain the most durability of the welding seam for practical use, the experimental design of this study adopts Taguchi method for determining a number of experiments. Each input parameter has 5 different levels. The result shows that the input parameters providing maximum tensile strength for welding in warp and weft directions are the following: the distance between a head of blower and workpiece (Dis) of 10 mm, the temperature of hot air (Tem) of 160 oC, the torque (Tq) of 9,000 N.mm, and the speed of hot air (Sha) of 4,000 mm/s. The maximum tensile strengths are 95.38 kN/m and 86.17 kN/m for warp direction and weft direction, respectively. After filtering the input parameters at the significance level of 0.05, the input parameters which significantly affect the strength of welding seam are the distance between a head of blower and workpiece, and the temperature of hot air. Additionally, the relationship between the input parameters and the strength of welding seams can be established. The comparison between the actual experimental data and the predicted values of the tensile strength for both welding directions shows that the average percentage error is less than 0.1% so that the forecast equation is appropriate for the explanation of the variables for this study and provide statistical reliability.  
Hotspot Location Identification Using Accident Data, Traffic and Geometric Characteristics
Get PDFDetermining the criterion for critical limits is always one of the essential challenges for traffic safety authorities. The purpose of identifying accident hotspots is to achieve high-priority locations in order to effectively allocate the safety budgets as well as to promote more efficient and faster safety at the road network level. In recent years, human, vehicle, road and environment have been recognized as the three main effective elements of the road transportation in the occurrence of accidents. In the present study, with combining the parameters related to accidents, geometric parameters of the accident location and traffic parameters, hotspots were identified by using the superior methods of Poisson regression and negative binomial distribution and based on the combined criteria of frequency and severity of accidents and equivalent damage factors. Then using Time Series Models in ANN, result were compared and validated. The results of ANN models demonstrate that the frequency method of accidents tends toward places with high traffic volume. MATLAB and STATA software were used. Non-native plumbing, curvature, slope, section length and residential area had more significance, and their coefficients indicated the significant effect of these parameters on the occurrence of the frequency and severity of accidents in hotspot locations
Finite Element Modelling of Concrete-Encased Steel Columns Subjected to Eccentric Loadings
Get PDFThis paper presents the 3D finite element (FE) analysis of the concrete-encased steel (CES) columns subjected to concentric or eccentric loadings. A new simplified technique of FE modelling that incorporates the concrete confinement behavior of the composite columns is proposed. This technique eliminates the need of predefining zones and constitutive properties of the confined concrete. After validated with past experimental data, the FE analysis is conducted to construct the strength interaction diagrams of the short CES columns. The effects of material properties including the compressive strength of concrete and yield strength of structural steel on the strength interaction diagrams of CES columns are numerically investigated. The FE results show that the concrete strength only has a significant effect on the column strength under combined compression and bending (compression phase) of the interaction diagram, while the yield strength of structural steel has a significant effect on both compression and tension phases. A comparison between the strength interaction diagrams predicted by FE analysis and the plastic stress distribution method specified in AISC360-16 “Specification for Structural Steel Buildings” shows that the design provision underestimates the strength of the short CES columns subjected to concentric or eccentric loadings. Such underestimation reduces as the compressive strength of concrete decreases or yield strength of structural steel increases
Prospect of Discharge at Daecheong and Yongdam Dam Watershed under Future Greenhouse Gas Scenarios using SWAT Model
Get PDFIn this study, the future expected discharges is analyzed at Daecheong and Yongdam Dam Watershed under Future Greenhouse Gas Scenarios based on RCM with 1 km spatial resolutions from Korea Meteorological Agency(KMA). HadGEM2-AO, which is the climate change prediction model that KMA recently introduced is used for this study. Geum river watershed area is 9,914.013 km2 and there are two dams, one of dam is Daecheong Dam completed in 1980, the other dam is Yongdam Dam completed in 2001. The runoff is simulated using the ArcSWAT model from 1988 to 2010. The simulation is in good agreement with measured data at the Yongdam Dam and Daecheong Dam showing R2 of 92.25% and 95.40% respectively. Using the average discharge from 2001 to 2010 as a baseline, the simulated annual average discharge increased by approximately 47.76% and 36.52% under the RCP4.5 scenario and RCP8.5 scenario respectively for the from 2011 to 2100
How Vehicle Types and Operator’s Legal Status Affect Safety of Interprovincial Buses in Thailand
Get PDFIn urgent response to an unenvied label as the world’ second worst road safety record, the Thai government has begun to ban the use of vans and double-decker buses for intercity bus services and is considering to change the legal status requirement of entities applying for bus operating licenses. This paper examines whether the empirical evidence justifies such policy directions. We use the Poisson and Negative Binomial regression models to examine whether vehicle types and legal status affect safety risks of intercity bus services, focusing on interprovincial routes outside Bangkok. The results confirm that the use of vans and double-decker buses significantly increases fatality risks of interprovincial bus services. But the results produce no evidence to support the claim that formal legal entities provide safer operation. While banning specific vehicle types for bus services is the right policy, our results caution that simply requiring bus operators to obtain formal legal status may not help improve safety performance. More effective policy options should focus on operational characteristics and vehicle standards
Synthesis and Characterization of Bimodal Mesoporous Silica Derived from Rice Husk Ash
Get PDFBimodal mesoporous silica (BMS) was obtained by synthesizing a silica derived from rice husk ash (RHA) with the structure-directing agents (Pluronic P123 and CTAB) using the sol-gel technique. RHA from biomass power plant was extracted with NaOH. The characteristic of BMS, UMS-P123, UMS-CTAB and RHS were performed with XRD, FT-IR, XRF, N2 adsorption-desorption isotherm, SEM and TEM techniques. As the result, BMS with large mesopore were obtained from the material like SBA-15 which are the dominant characteristic of Pluronic P123, and incorporated of CTAB, which the small mesopore were original from the parent templates. BMS shows higher specific surface area (>700 m2/g) pore volume (1.30 cm3/g) and pore size (9.20 nm) than the unimodal mesoporous silica (UMS-P123 and UMS-CTAB). Therefore, BMS synthesized from rice husk ash had the excellent material that could find the applications in adsorbent and also gave environmental benefits and renewable resource
Capacity Enhancement of Enterobacter aerogenes for Heterotrophic Nitrification in Integrated Fixed Film Activated Sludge (IFAS) Wastewater Treatment Process
Get PDFEnterobacter aerogenes was found recently as a high capacity bacterium for degrading acrylamide (AM) in the culture media. The AM biodegradation was inhibited by free ammonia nitrogen due to the failure of heterotrophic nitrification in the sequencing batch reactor (SBR) wastewater treatment system. In this study, the heterotrophic nitrification of E. aerogenes was enhanced with IFAS technology using BioPortz moving media operated at the solids retention time (SRT) of 9 days and temperature of about 28 oC. The experiments were conducted comparatively in the conventional activated sludge (AS) and IFAS systems containing either mixed culture bacteria or E. aerogenes for autotrophic and heterotrophic nitrifications, respectively. The results revealed that E. aerogenes could be enhanced with IFAS technology to complete heterotrophic nitrification. There was no significant difference in nitrification between AS and IFAS systems of two microbes if the systems were properly operated. Ammonia stripping was found in the AS systems whenever nitrification was failed and CO2 was stripped out, resulting in the increase of pH. The clogging of BioPortz media with calcium carbonate precipitates reducing the IFAS performances was firstly reported as a result of operating the IFAS systems at the relative high temperature and moderate hardness
The Integrated Appraisal Framework of Rural Road Improvement Projects
Get PDFThe government policy for Thailand to be a logistics and transportation hub presents challenges to the Department of Rural Roads (DRR). The Bureau of Rural Roads (BRR) 11, 12, and 14 as the subsidiaries of the DRR have been enforced to reform their methods of appraising rural road improvement projects. Multi-criteria decision-making (MCDM) was first developed but was found to be inappropriate within the fiscal constraints since it was not based on monetary terms. This paper explores the DRR’s attempts to overcome this problem. The DRR conducts a Benefit-Cost Analysis (BCA) to filter the improvement projects prioritized under the MCDM approach. While calculation is not a problem under BCA, the method cannot be readily adapted to incorporate all relevant parameters particularly those relating to the social benefits of road improvement projects. These parameters are important in the Thai context and compatible with the characteristics of rural roads. The findings reported demonstrate that the incorporation of factors taken into account in MCDM but overlooked in traditional BCA is currently impracticable in view of the lack information and difficulty of expressing those parameters in monetary terms. The paper discusses supplementing the DRR’s improvement project appraisal process by BCA methods thus enhancing the effective and transparent allocation of the DRR’s budget, while simultaneously providing regional benefits
Stabilized Oily-Emulsion Separation Using Modified Induced Air Flotation (MIAF): Factor Analysis and Mathematical Modeling
Get PDFThe objective of this work was to study the treatment of oily-wastewater by the combination of induced air flotation and coagulation or the modified induced air flotation (MIAF). Effects of bubble hydrodynamics and mixing were analyzed along with the treatment performance for separation different stable oily wastewaters, including cutting oil, lubricant oil, palm oil. The results suggested the necessity of coagulation for the efficient separation of these emulsions. Different alum concentrations were required for good separation due to the variation of oil concentration. The maximum efficiencies of higher than 85% can be attained under the optimal air flow rate of 0.3 L/min air flow rate for 10 minutes with appropriate alum dosage. Moreover, the result from factor analysis indicated the importance of coagulant dosage, mean droplet size, and hydrodynamic condition in term of a/G ratio on the treatment performance. Both individual and jointed impacts of these parameters on the separation efficiency can be seen. Finally, a good correspondence was obtained from the experimental data and the mathematical modeling at which identified the correlation between the treatment efficiency and these key factors with the mean absolute percentage error (MAPE) of at 14%