Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Production of Composite Fibers from Natural Rubber and Lignin
Get PDFThe interest of natural rubber (NR) product applications have been increased as natural rubber can be obtained from nature and it can be produce into sustainable products. It’s widely used in applications such as tires, wires, latex products, medical devices, and sport components. In this work, the use of electrospinning technique to produce fibers has been carried out because this technique has been proved to be a simple and effective technique for fiber production. This work aimed to study morphology, diameter, and functional group of natural rubber fibers, DPNR fibers, and different loadings of lignin in DPNR/lignin composite fibers produced by electrospinning technique. The condition for electrospun fibers were as following; needle-target distances of 15 cm and flow rate of 2.5 ml/h. The results of deproteinization by urea, SDS solution, and acetone showed protein in NR latex decreased. Moreover, increasing load of lignin resulted in an increase of the diameter of DPNR/lignin composite due to increasing of viscosity of the solution related to increasing of viscoelastic force. Characterizations of these fibers were reported using scanning electron microscopy to examine fibers surface and measure diameter of the fibers. Fourier transform infrared spectroscopy was used to examine the functional group of the fibers
A Two-Stage Anaerobic Digester of Pig Manure and Food Waste for Biogas Production with Heat Exchanger
Get PDFPig manure is one of the most significant causative agents of environmental pollution in swine farm areas. To reduce this problem, research has suggested the use of piggery waste for sustainable energy production. The aim of the present study was to investigate the effects of feedstock ratio on the efficiency of 2-stage anaerobic co-digestion. A 100-L capacity digester was built with the variation of mixing ratios of pig manure to food waste to water of 50:20:30, 35:35:30 and 20:50:30, respectively. Biogas production at high temperature using hot water heating system was also investigated. The effluent in fermentation tank was collected every 5 day and analyzed for the following parameters: total solid (TS), suspended solid (SS), total dissolved solid (TDS), amount of fat oil and grease, and biological oxygen dissolved (BOD). The results revealed that feedstock with the mixing ratio of 50:20:30 and 35:35:30 produced high volume of biogas. The anaerobic digester under hot water treatment (40 oC) exhibited higher biogas volume than that under normal temperature (30 oC). The ratios of feedstock also affect the efficiency of anaerobic digester as indicated by the difference in the reduction of TS, SS, TDS, COD, BOD and fat oil and grease
Optimal Assignment of Customer-Desired Items to the Fetching Robots in Superstores
Get PDFThis paper discusses a task assignment problem. The scenario under consideration is a superstore with a team of fetching robots. There is a set of customers each requiring a unique set of items. The goal is to assign the task of fetching the items to the available robots in such a way that the time and effort required for fetching the item is minimized. For this purpose, a Markov Decision Process based model has been proposed. The proposed-model is solvable using stochastic dynamic programming algorithms such as value iteration for the calculation of optimal task assignment policy. The analysis of the characteristics of the resulting optimal policy has been presented with the help of a numerical case study
Recovery of Moringa oleifera Oil from Seed Cake by Supercritical Carbon Dioxide Extraction
Get PDFCommercial Moringa oleifera seed oil has been currently produced via mechanical extraction using a screw press machine. Approximately 30 %wt. of the residue oil remains in the seed cake. Thus, this study aims to examine the effects of pressure and solvent-to-feed (S/F) ratio on the supercritical CO2 extraction of seed cake obtained from mechanical extraction. The antioxidant activities of extracted oil were determined using the standard in vitro biological assays. The supercritical CO2 extraction duration of seed cake is shortened because the mechanical extraction reduces oil content before performing supercritical CO2 extraction. At 50 °C and 30.0 MPa, S/F ratios of 0.4 /min and 1.0 /min have corresponded to an extraction duration of 300 min and 180 min, respectively. Up to 90 %wt. of the oil content in the seed cake can be recovered at 30.0 MPa, 50 °C, and after 200 min of extraction duration. Regardless of the extraction pressure, the antioxidant activities of M. oleifera seed oil were maximized at 60 °C
Effect of Labral Tear, Repair and Reconstruction on Strain Distribution in Hip Joint
Get PDFLabral tear can be caused by degeneration or traumatic hip dislocation. It can be treated by mainly two surgical options: labral repair and labral reconstruction by using tissue reconstruction (iliotibial band), depending on the tear size. Finite element analysis was, thus used to simulate strain distribution in different conditions, namely intact labrum, labral tear, labral repair and labral reconstruction, varied under walking and stair-climbing conditions. By applying labral repair, the labrum thickness was reduced, resulted in increased the average maximum strain on labrum tissue by 21.36% compared to torn labrum, while labral reconstruction reduced the average maximum strain through load sharing of iliotibial band by 28.49% compared to torn labrum and 41.21 % compared to labral repair. The equivalent of total strain of the varied cases did not exceed 25,000 microstrain, not causing bone fracture. The hip model was validated by measuring the normal contact force at the hip joint of a cadaver using hip simulation machine and compared with the simulation result. The simulation result corresponded to the validation test
Gravitational Search and Harmony Search Algorithms for Solving the Chemical Kinetics Optimization Problems
Get PDFThe article is dedicated to the analysis of the global optimization algorithms application to the solution of inverse problems of chemical kinetics. Two heuristic algorithms are considered - the gravitational search algorithm and the harmony algorithm. The article describes the algorithms, as well as the application of these algorithms to the optimization of test functions. After that, these algorithms are used to search for the kinetic parameters of two chemical processes – propane pre-reforming on Ni-catalyst and catalytic isomerization of pentane-hexane fraction. For the first process both algorithms showed approximately the same solution, while for the second problem the gravitational search algorithm showed a smaller value of the minimizing function. Wherefore, it is concluded that on large-scale problems it is better to use the gravitational search algorithm rather than the harmony algorithm, while obtaining a smaller value of the minimizing function in a minimum time. On low-scale problems both algorithms showed approximately the same result, while demonstrating the coincidence of the calculated data with the experimental ones
Optical Fiber Biosensor toward E-coli Bacterial Detection on the Pollutant Water
Get PDFIn this study, Zinc oxide (ZnO) nanorods based fiber optic biosensor has been reported for rapid and sensitive detection of Escherichia Coli (E-coli). A thin layer of Gold nanoparticles (Au) (around 50 nm) is coated on the tip of a multimode plastic optical fiber. ZnO Nanorods are grown on Au layer thorough hydrothermal technique. This sensor showed a very fast response within the first 10 second of contacting the present of polluted water with E-coli Different concentrations of E. coli from (1000 to 4000 CFU/ml) have been tested and a sharp trend of sensitivity was observed. This sensing platform shows promising potential for regular water and food quality monitoring of various pathogenic microorganisms
Hierarchical Decentralized LQR Control for Formation-Keeping of Cooperative Mobile Robots in Material Transport Tasks
Get PDFThis study provides a formation-keeping method based on consensus for mobile robots used in cooperative transport applications that prevents accidental damage to the objects being carried. The algorithm can be used to move both rigid and elastic materials, where the desired formation geometry is predefined. The cooperative mobile robots must maintain formation even when encountering unknown obstacles, which are detected using each robot's on-board sensors. Local actions would then be taken by the robot to avoid collision. However, the obstacles may not be detected by other robots in the formation due to line-of-sight or range limitations. Without sufficient communication or coordination between robots, local collision avoidance protocols may lead to the loss of formation geometry. This problem is most notable when the object being transported is deformable, which reduces the physical force interaction between robots when compared to rigid materials. Thus, a decentralized, hierarchical LQR control scheme is proposed that guarantees formation-keeping despite local collision avoidance actions, for both rigid and elastic objects. Representing the cooperative robot formation using multi-agent system framework, graph Laplacian potential and Lyapunov stability analysis are used to guarantee tracking performance and consensus. The effectiveness and scalability of the proposed method are illustrated by computer simulations of line (2 robots) and quadrilateral (4 robots) formations. Different communication topologies are evaluated and provide insights into the minimum bandwidth required to maintain formation consensus
Deep Learning Based Thermal Image Processing Approach for Detection of Buried Objects and Mines
Get PDFThermal imaging based mine detection technique is widely adopted due it suitability of detecting buried metallic and also non-metallic land mines in battle fields. Accurate mine detection using thermal images depends on thermal contrast between the soil and mine and it is affected by various factors such as the depth of burial; soil properties and attributes, water content in the soil, mine properties; as well as the time of day of image acquisition. With temporal temperature variations of the soil, it is difficult to distinguish and discriminate between the buried object and the background in the thermal image using the conventionally followed binary thresholding approach in gray scale. This paper presents deep learning region convolution based neural network approach to identify the buried objects in thermal images. A region interest selection using a bound box is followed for identifying the buried object in the thermal image. From the experimental results, it is found that there is temperature variation in the thermal images of the buried objects due to the change in heat carrying capacity of the surround soil. Proposed neural network method showed 90% accuracy in predicting the target locations of buried objects in the thermal images and it can be extended for land mine detection using thermal image processing approach
Operational Models, Drivers’ Compensation, and Bus Service Quality in Bangkok
Get PDFThis paper explores how operational models and compensation methods are associated with bus drivers’ incentives and consequently bus service quality and safety in Bangkok. We cross-analyze data on bus drivers’ compensation collected from a structured interview survey with data on passenger complaints and bus accidents compiled from governmental databases. Recognizing that the official statistics on bus accidents in Bangkok are undercounted, as the government includes only accidents with severe damages and injuries, we use passenger complaints as the proxy for safety levels. We find that private joint-service operators provide their drivers with far less compensation and benefits than the state-owned operator. The private operators also tie drivers’ compensation and benefit levels to the numbers of working hours and trips, especially on routes where private operators can compete freely. These compensation methods incentivize drivers to work long hours beyond what is permitted by law, inducing fatigue and potential accidents. The key policy implication is that the bus policy aiming to improve service quality and safety should improve drivers’ compensation and working conditions