Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Design and Analysis of the Slider Shear Test System Using Nested GR&R Measurement System
Get PDFThe shear strength of the adhesive bonding between slider and suspension is a vital characteristic for head gimbal assembly. The current shear test method has shown improper failure modes; therefore, a new system has been designed to improve the slider shear test. Six sigma framework was applied to redesign the slider shear test system. The finite element method confirms that new design concept is acceptable because it can yield the correct failure mode of shear test. Next, the measurement errors of the new shear test system are assessed using nested gage repeatability and reproducibility (NGR&R). NGR&R of new shear test system is less than 10% which is an adequate gage. Then, the results of simulation also confirm that decreasing of measurement error can significantly reduce the over reject rate. In conclusion, new shear test system can be effectively used to reflect the real product quality and to obtain more accurate process capability resulting from the correct failure mode of testing
A Comprehensive Review of Thermal Control of Moveable and Non-Moveable Spacecraft in Mars Sample Collecting Mission
Get PDFSpace exploration has been the focus of scientists for centuries. Among all the planets, Mars is the closest to our planet that has the potential of discovering traces of life signs. The planet has critical environmental conditions which are from either the planet itself or the Sun. Nowadays, there are several spacecrafts sent to Mars for specific purposes. One of the current missions is Sample Collecting Mission, which collects Mars samples and sends them back to Earth. A current rover for this mission, Perseverance, was launched by NASA with the main purpose of collecting samples on the planet for at least a two-year mission period. Sample Retrieval Lander will be operated within around six months for receiving the samples collected by the rover and sending them back to the Earth. Each spacecraft also needs different kinds of power sources and thermal management systems based on their mission objectives and periods. The overview and consideration points for selecting each source of power and thermal control are investigated and discussed based on our perspectives
Modelling and Feedforward Control of Pulsed Bed Adsorption Column for Colorant Removal in Sugar Syrup
Get PDFIn sugar refining, pulsed bed adsorption columns are used to remove colorants in sugar syrup. The pulsed bed adsorption column is a cyclic steady state operation that maximize the adsorbent utilization due to the increased driving force but requires special attention on control and optimization. The modelling and feedforward control of the pulsed bed adsorption columns is investigated in this article. The aim of this research is to develop the mathematical model of pulsed bed adsorption column by using the parameters obtained from breakthrough of fixed bed column and to investigate the optimum cycle time at different colorant concentrations in feed sugar syrup. The analysis showed that the optimum cycle time of pulsed bed adsorption column depended on feed flow rates and the colorant concentrations in feed sugar syrup. As the feed flow rate and colorant concentration increased, the optimum cycle time decreased. The feedforward control successfully compensated the effects of disturbances from colorant concentrations in feed syrup for both step and cosine functions and yielded the sugar syrup that met its specification
Weight Functions for Edge Crack in Bilayer Material
Get PDFThe problem of weight functions for an edge crack in semi-infinite bilayer materials was revisited. The research aimed to develop the empirical equations for geometrical factors for reference SIFs associated with the weight functions, which covered a wider range of elastic mismatches. The weight functions in consideration covered the cases of a crack tip in a surface layer as well as in a substrate. The direct adjustment method was employed to derive the weight function coefficients. The reference SIFs for calculating the weight function coefficients were determined by finite element analysis with a systematic variation of the crack depth and the elastic mismatch parameters. The accuracies of the empirical equations for geometrical factors for the cases of a crack tip in coating and substrate were better than 1.3% and 4%, respectively. The weight functions were applied to bilayer materials with an edge crack under various crack face loading profiles. The SIFs predicted by the weight function method agreed with those from the FE method or the literature
Review of Non-Thermal Plasma Technology for Hydrogenation of Vegetable Oils and Biodiesel
Get PDFThe hydrogenation of lipid derivative compounds has received much attention as it is one of the key chemical reactions of industrial processes to improve the physical and chemical properties of those compounds such as thermal resistance, cold flow properties, oxidative stability, etc. The principle of hydrogenation of vegetable oil for margarine production relies on the addition of hydrogen to the carbon double bond positions of fatty acid molecules to become a single bond, increasing the saturated fatty acids until the texture becomes semi-solid. The partial addition of hydrogen to biodiesel improves its oxidation resistance. At present, industrial-scale using catalytic hydrogenation of lipid derivative compounds operates under high temperature and high-pressure environments, leading to a high trans-fat content in the products and requiring catalyst separation from the product. Non-thermal plasma (NTP) technology as a green process can be deployed to substitute conventional hydrogenation, on a laboratory scale for the time being, because no catalyst is required and the process can occur at near ambient temperature and low or atmospheric pressure. Moreover, trans-fat formation is several times lower than that of catalytic hydrogenation. The present review article provides more insight into the various types of NTP technology for lipid derivative compounds hydrogenation, including discussions on different experimental setup configurations, parameters affecting plasma hydrogenation, properties of synthesized products, as well as the advantages and drawbacks of environmentally-friendly plasma hydrogenation compared to conventional catalytic hydrogenation
Quality Improvement of Low-Grade Calcium Carbonate Using Induced Roll Magnetic Separator
Get PDFCalcium carbonate (CaCO3) is an essential raw material in the manufacture of goods and industrial products like cement, rubber, paper, paints, food, and medicines. For this compound to be economically valuable, however, its quality needs to meet the standard market requirements. Among the various impurities found in natural CaCO3-bearing ores, iron (Fe) is one of the most problematic. In this study, the upgrading of low-grade CaCO3 from a processing plant in Thailand by magnetic separation was investigated. Detailed characterization of the low-grade material was also carried out to identify the solid-phase partitioning of Fe. The results showed that Fe was mainly associated with magnetite and pyrrhotite in the ore, and during processing, additional Fe was introduced from the ball milling process. To improve the quality of this low-grade CaCO3, the effects of magnetic field intensity, feed rate, and repetition on the induce roll magnetic separation were investigated. Based on the results, higher magnetic field intensity, lower feed rate, and more repetition are required for the upgrading of low-grade CaCO3
Developing an Optimal Brain Computer Interface Model using Functional Near Infrared Spectroscopy: A Review
Get PDFBrain-Computer Interfaces (BCIs) are promising in advancing numerous applications. Although many functional near-infrared spectroscopy (fNIRS)-based BCIs have been studied, the development of an optimal fNIRS-based BCI model remains unclear. This study aims to review recent methodologies that used to optimize fNIRS-BCI models in four aspects i.e. signal acquisition, pre-processing, feature extraction, and machine learning. Besides, the differences, strengths, and limitations of various algorithms are discussed and highlighted. By comprehensively examining the recent trends and challenges in fNIRS BCI model development, this study proposes and discusses potential techniques in advancing fNIRS-based BCIs model development. The results suggest that future fNIRS-based BCI studies should focus on addressing cross-subject classification challenges and real-world fNIRS-BCI applications
Effect of Curing Temperature and Free Lime Content in Fly Ash on Basic Properties and Autoclave Expansion of Fly Ash Mixtures
Get PDFThis study incorporates a detailed experimental program executed to determine the degree up to which the autoclave expansion of fly ash mixtures is sensitive to curing temperature. Three types of fly ashes were used and free lime was applied to increase the free lime contents in different fly ashes up to 10%. The influence of curing temperature on autoclave expansion of the mixtures was evaluated by curing under two temperatures, i.e., 23°C and 29°C for 24 hours after mixing. Experimental results exhibited that a higher free lime percentage resulted in a higher magnitude of autoclave expansion. It was observed that at a curing temperature of 23°C, the autoclave expansion was higher than the expansion of samples cured at a temperature of 29°C. Most of the mixtures, except the mixtures containing 40% fly ashes with the free lime amount of 10% and cured at a lower curing temperature, showed autoclave expansion values below the allowable limit recommended by ASTM C618
Note on Fourier Transform of Hidden Variable Fractal Interpolation
Get PDFThis paper investigates the Fourier transform of a hidden variable fractal interpolation function with function scaling factors, which generalizes the Fourier transform of hidden variable fractal interpolation function with constant scaling factors. Furthermore, the Fourier transform of quadratic hidden variable fractal interpolation function with function scaling factors is also investigated. With an aim of maximizing the flexibility of hidden variable fractal interpolation function and quadratic hidden variable fractal interpolation function, a class of iterated function systems involving function scalings is chosen for the present study
Thin Layer Drying Kinetics and Mathematical Modeling of Moisture Diffusivity in Cocoa Pod Husk (CPH)
Get PDFCocoa pod husk (CPH), an agricultural by-product of the cocoa separation process, contains an average moisture content of 5.40 ±0.05 kgwater/kgdry matter. Drying characteristics of CPH were examined in hot air at 50, 60 and 70°C using a laboratory oven with air ventilation at 3 L/min and a load cell sensor (HX-711) was used for weight loss tracking. Twelve mathematical models simulated the drying rate from a drying curve at each operating temperature by comparing four statistically calculated parameters. Levels of variation were investigated by plotting experimental data against the predicted moisture ratios to identify the sum of residuals and obtain a good fit. The Midilli et al. model provided the best drying characteristics with optimized statistical parameters. Using an Arrhenius type relationship, the effective diffusivity coefficient of moisture transfer varied from 7.979 x 10-10 to 13.298 x 10-10 m2/s, with operating temperature set at 50, 60 and 70°C and activation energy for moisture diffusion 70.48 kJ/mol