Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
Not a member yet
1223 research outputs found
Sort by
Finite Element Analysis of the Mechanical Behaviors of Endodontic Nickel–Titanium Rotary Files: A Review
Get PDFAn endodontic rotary file is a special instrument used in the treatment of dental pulp and surrounding tissues. They are available in a wide range of sizes and configurations, specifically tailored to accommodate the narrow and curved root canals of the teeth. Consequently, dental rotary files are slender, flexible, and generally made of a nickel-titanium alloy. The investigation of mechanical behaviors of dental files can be effectively conducted using computational approaches, such as the finite element method. This numerical tool is widely used in many engineering applications, especially for solid mechanics and structural problems. With the finite element method, the reliability and safety of dental files can be preliminarily assessed in a short period of time. This report reviews applications of the finite element analysis method to investigate the mechanical responses of endodontic rotary files. Both the finite element modeling of the files and applications of the method to rotary file problems are included in the study. This review includes the stress distribution, flexibility and stiffness, and fatigue life of the files. There have been a variety of approaches to model files under flexural and torsional loads. Static analysis with simple loading conditions was adopted in most of the studies. The analytical approach can be improved so that files under working conditions are accurately modelled. Moreover, there is a need for verification of the finite element solutions with experimental or clinical studies
Exploring ASEAN Fly Ash for Enhancing Cement Hydration and Service Life Prediction of Portland Cement Mortar
Get PDFThe durability of cementitious materials can be improved with the widespread utilization of fly ash (FA). Although FA has been available for use in cement and concrete industries for decades, there is still a practical barrier associated with its application. The difficulty stems from its wide variety and heterogeneity. The purpose of this research is to conduct both experimental and numerical investigations to achieve a better understanding of managing the variation of FA, which reflects its durability. The chemical properties and particle size distribution of FA from five distinct sources in ASEAN region were analyzed. In addition, the degree of reactivity, flow, toughened porosity, and apparent chloride diffusivity coefficients of blended FA-cement systems were studied (Da). The Life365 service life model was executed. Using analysis of variance (ANOVA) and sensitivity analysis using linear regression, the experimental outcomes were statistically examined. Having a 15% FA replacement level resulted in a roughly 70% decrease of the Da value, extending its serviceability by around 13%. The chemo-physical processes in multi-scale structures were shown to be the most important element by statistical analysis, and the degree of response in blended FA-cement systems and its toughened porosity were found to be among the most beneficial aspects affecting its durability
Practical Implementation of Lean Management Techniques and Ergonomic Consideration to Improve Manual Assembly Process During the COVID-19 Crisis
Get PDFThis research focused on the cycle time reduction of the automotive audio monitor base frame assembly process in a small electronic parts manufacturing company through the application of the Lean and ergonomics approaches. In recent years, the company has faced the problem of not being able to assemble products to meet customers’ orders due to the need to lay off some skilled workers to survive during the COVID-19 crisis. This resulted in a severe loss in customer goodwill and confidence. The improvement process began with a review of the current assembly workflow as well as the detailed hand and arm movements of workers. Then, to determine the as-is operational procedure and average cycle time of the assembly process, a series of videos were recorded and playback in slow motion. Lean management techniques, such as 7 wastes and 5 Whys, were employed to identify the potential root causes of the problems. In addition, the ECRS (eliminate, combine, rearrange and simplify) techniques of Lean management in combination with the ergonomics principles were applied to modify the operational procedure and the postures and movements of the workers. The workspace and environmental conditions were also adjusted to enable more efficient workers’ operations. The result demonstrated that such an approach could help reduce the cycle time of the assembly process to achieve the predefined target
MorphoNet: A Novel Bivalve Images Classification Framework with Convolutional Neural Network
Get PDFThe bivalves' morphometric analysis of the freshwater shell characteristics is based on the shell size, shape, tooth, scars, and texture. We experimented and compared the accuracies of the following popular convolutional neural network architectures: ResNeSt, MobileNet, VGG16, Transfer Learning, and EfficientNet, whose model trainings are based on the bivalve image dataset obtained from a biology laboratory. The MobileNet model that gives the highest accuracy rate by 72% is selected to be a classification model of our framework named MorphoNet. We also applied the YOLO4 object detection in the MorphoNet to detect the teeth and scars on the bivalve image. The framework can identify the bivalve class labels and detect the interesting features on the bivalve images automatically. It is an alternative tool to help the biologists in a preliminary class label identification and support the land-marking creation and morphometric analysis instead of doing it by hand
Electricity Generation from Single Chamber Microbial Fuel Cells using Granular Activated Carbon as Anode for Wastewater Treatment
Get PDFLocally sourced granule-activated carbon (GAC) has been used in wastewater treatment systems, but it is not widely used in single chamber microbial fuel cells (SCMFCs). The GAC in an anode coupled with a carbon cloth was used in the SCMFCs in this research, with 1.00-L of the GAC added to the carbon cloth in the anode. Three SCMFCs were operated in continuous flow mode. The synthetic wastewater was prepared from rice flour dissolved in tap water, with a chemical oxygen demand (COD) value of 1,816.32 ± 204.78 mg/L. The organic loading rates (OLRs) in the study were 0.91, 1.82, and 7.27 kgCOD/m3-d. The maximum power density levels generated by the three SCMFCs were 13.16, 7.96 and 4.11 mW/m2 from OLRs of 0.91, 1.82, and 7.27 kgCOD/m3-d, respectively, and the efficiency rate of COD removal were 24.96%, 24.85%, and 20.75%, respectively. This research also presented a voltage boost converter circuit for charging a 0.25F storage supercapacitor. Only two OLRs provided an electric voltage that could run the circuit (0.49V and 0.45V generated by OLRs of 0.91 and 1.82 kgCOD/m3-d, respectively.) The supercapacitor set was charged to reach the maximum output of 5.25 V taking 19.5 hr and 37.5 hr, respectively
Erosion-Corrosion Simulation of Thermally Sprayed WC-Based Cermet in Artificial Seawater and Dam Water Environments
Get PDFMechanical equipment operated in a water dam environment is at risk of erosion-corrosion. To address this issue, thermally sprayed cermet coatings are an adequate solution for increasing resistance to corrosion and wear in hydro turbines, especially with high river sedimentation loads such as those in Cirata and Jatiluhur dams in Indonesia. In this study, WC-based cermet coatings with WC-10Co-4Cr and WC-12Co respectively were coated on AISI 1030 steel substrate and evaluated in media simulating the Cirata and Jatiluhur water dam environments, as well as in simulated seawater conditions. The morphology and structure of the sprayed coating were analyzed by SEM and XRD, and microhardness, porosity, and surface roughness were also studied. The corrosion resistance of the coating was evaluated using potentiodynamic polarization. More importantly, erosion-corrosion resistance in seawater simulations studied by Closed Flow Loop System (CFLS) equipment utilizing coupon tests was also explored. The results showed that the WC-10Co-4Cr coating has good electrochemical corrosion resistance with less erosion-corrosion compared to the WC-12Co coating, at 0.06-0.15 mm/year and 0.16-0.26 mm/year, respectively. Coatings with Cr content show a lower corrosion rate due to the formation of stable WCr2O6 and W18O49 oxides, making them a good choice for coating hydro turbine components
Case-based Maintenance Model for handling Relevant and Irrelevant Cases in Case-based Reasoning System
Get PDFCase-based maintenance can be resource intensive and requires significant time and effort to collect and analyse all cases. This can lead to inefficiencies and high costs in the entire case-based reasoning system. Accordingly, the Relative Coverage Condensed Nearest Neighbour had been created to reduce the number of cases in a dataset by selecting a subset of representative cases, whereas maintaining the overall performance of the whole system. Besides, Footprint utility deletion is a type of case deletion algorithm that can remove redundant or irrelevant cases from a storage, though maintaining the system’s competency. Recently, Hybrid approach was given to ensure that the case-base remains up-to-date and relevant, while also reducing its size and complexity. However, the results from using these approaches seem to be improved for the better performance. Therefore, the proposed model is developed, which comprises two main phrases by using case-based reasoning and identifying relevant and irrelevant cases to provide better results. The reduction size of case-base is lower than the traditional studies approximately 1-9% and also gives higher percentage of solving problems about 1-7%, while the average problem-solving time is shorter than them nearly at most 8 times.  
Accuracy Verification of a Smartphone-Based PPK GNSS Surveying Technique and Earth Volume Determinations
Get PDFRaw global navigation satellite system (GNSS) measurements from a smartphone are used for position determinations as they can be extracted from the Android operating systems together with Thailand Department of Lands (DOL) provide network real-time kinematic GNSS correction services; hence, enabling cheaper and more compact for high precision solutions. This study applies the GNSS raw observations obtained from a smartphone in order to determine positions and later compute an Earth volume based on obtained positioning results as Thailand constructions are increasing in different scales and earthworks is one of the primary works. The experimental area is 11,145 square meters with 21 ground markers. GNSS signals are measured every 1 second at 1-hour observation period. Computed observations from a smartphone provide relatively optimal horizontal and vertical positioning accuracies of 4 and 8 centimetres with the longest convergence time of 40 minutes. Differences between the determined Earth volumes using the smartphone-based and traditional surveying technique do not exceed 10%. The estimated manhour and equipment cost are efficient can lead to 90% reduction. Performances are demonstrated and assessed on actual earthwork computations. Future work may apply estimated smartphone-based network real-time kinematic (NRTK) and post-processed kinematic (PPK) positioning solutions as ground control points for other earthwork determinations through aerial photography
Plasma Activated Soil: A Novel Technique for Agricultural Soil Enhancement
Get PDFIn this work, the influence of atmospheric-pressure air plasma on soil quality improvement has been studied. The practical plasma model has been designed to shape like a rake using spark plugs. The high-frequency AC high voltage has been varied at 9, 12, and 15 kV for plasma generation. The soil has been treated directly with air plasma for three consecutive days with a discharge time of 15 and 30 minutes once a day before using it for cultivation. Regarding the experimental results, air plasma significantly positively affects soil enhancement. The germination rate and length of the sprout of all the morning glory seeds cultivated in the plasma-treated soils have been higher than the one of the control group, which are up to 1.74, and 1.14 times higher than that of the control group, respectively. From the soil analysis, the Total Kjeldahl Nitrogen (TKN) content could be improved for all the plasma-treated cases. The best condition has been at 12 kV with a discharge time of 15 minutes, where the TKN has been 4.33 times greater than the one of the control group. Moreover, the pH of all the plasma-treated cases has tended to increase, resulting in more pH-balanced soils
Exploring Qualitative and Quantitative Decoration on Amine-Modified Mesoporous Silica for Enhance Adsorption Performances
Get PDFUsing the triblock copolymer Pluronic F127 as a surfactant, tetraethyl orthosilicate (TEOS) as a silica source, and hydroxylamine hydrochloride as an amine source, a group of amines-modified mesoporous silica Santa Barbara Amorph-16 (SBA-16) materials with different template withdrawal methods and amine loading concentrations were prepared through sol-gel conditions. The investigation will provide qualitative and quantitative information on amine-modified SBA-16 decoration with a brief overview of the non-destructive analysis methods for advanced materials as adsorbent candidates. Highly ordered mesostructured amine-modified SBA-16 materials were prepared using high-temperature (or calcination) and solvent extraction de-templating methods. Mesostructured amine-modified SBA-16 has been successfully examined using a Synchrotron Radiation Low-Angle X-ray Diffraction (SR-LXRD) instrument for phase identification, Small-Angle Synchrotron X-rays Scattering (SAXS) for identifying structural changes in a porous material, Fourier Transform Infrared (FTIR) for identifying functional groups, Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) elemental analyzer for determining the number of silica, oxygen, and nitrogen elements, and a Specific Surface Area (SSA) analyzer for measuring the specific surface areas. The SR-LXRD and SAXS results demonstrated that the synthesized novel materials were defined unambiguously as a bi-continuous cubic body center Im3m mesostructured. FTIR and SEM-EDS analyses verified that the amine groups were uniformly deposited on the SBA-16 surface. The SSA analyzer results also clarified that the novel materials exhibited ordered and meso-framework amine-modified SBA-16 with a large surface area. Novel materials can be considered high-potential uranium adsorbent candidates. Preliminary adsorption investigations have shown that the amine-modified SBA-16 materials can adsorb uranium in natural seawater showing an uptake capacity of as much as 24.48 mg-U/g-adsorbent