Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Buckling Analysis of Nonlocal Nanocolumns Using Finite Element Method
Get PDFThis research introduces a finite element method, considering size-dependent effect via nonlocal elasticity to analyze the buckling load of columns subjected to concentrated, distributed, and combined load cases. Two types of columns are considered: columns with a constant moment of inertia and nonuniform cross-section. The end conditions of columns comprise the following: clamped-free, hinged–hinged, clamped–hinged, and clamped–clamped. This paper illustrates the computational results using the relationship between buckling load normalized via the classical eigenvalue buckling load. The current findings show that the buckling load dramatically decreases at the normalized material length scale between 1 and 10. The most and least considerable effects on buckling load reduction are clamped–clamped and clamped-free end conditions. For the case of combined loads, a buckling concentrated load decreased proportionally as applied uniformly distributed force increased. An increase in concavity (or convexity) of parabolic columns will influence the buckling of the concentrated and uniformly distributed buckling loads
Synthesis and Adsorption Performance of Graphene Oxide-Polyurethane Sponge for Oil-Water Separation
Get PDFGraphene oxide was prepared from pencil type 2B by modified Hummers method and used for coating of polyurethane sponge. The graphene oxide-modified polyurethane (GO/PU) sponge was applied as an adsorbent for oil-water separation, which was represented by the removal of diesel oil from water. The formation of graphene oxide and GO/PU was characterized by spectroscopic, imaging, and X-ray diffraction methods. The best adsorption performance of GO/PU was 71.2% efficiency within 10 s of contact time. It was demonstrated that the incorporation of graphene oxide enhanced the adsorption performance of the PU sponge which showed 54.9% efficiency diesel removal from water under the same experimental condition. The result also suggested that graphene oxide (GO) has a synergistic effect of superhydrophobicity and good mechanical performance in the GO/PU sponge
Constrained Joint Replenishment Problem with Refrigerated Vehicles
Get PDFWe study a constrained joint replenishment problem with a multi-commodity refrigerated road transport in cold chain logistics. Each truck may have multiple temperature zones, since products in full truckload shipment may have different temperature requirements. In the proposed mathematical programming model, we want to minimize the expected total cost that includes the inventory cost and the transportation cost as well as the penalty cost if temperature violation occurs subject to the full truckload constraint. Under the deterministic demand, the cycle time of each product, the temperature of each zone in each truck and the allocation plan (the number of units of each product to be shipped in each zone in each truck) are obtained from the mixed-integer nonlinear optimization model. Under the stochastic demand, we assume that the inventory is controlled using a periodic review system, and the order-up-to level is chosen to maintain the desired cycle service level of each product. In the case study of one of the largest modern grocery retailers in Thailand, our model is applied to obtain the optimal replenishment policy. Currently, the company's fleet consists of single-temperature trucks. We estimate the monetary benefit obtained by switching from a single-temperature truck to a multi-temperature truck. We also estimate the cost reduction from reducing the lead time. Finally, our model can be used to quantify the trade-off between the service level and the inventory cost to help the company choose the appropriate service levels
Real-Time Induction Motor Health Index Prediction in A Petrochemical Plant using Machine Learning
Get PDFThis paper presents real-time health prediction of induction motors (IMs) utilised in a petrochemical plant through the application of intelligent sensors and machine learning (ML) models. At present, maintenance engineers of the company implement time-based and condition-based maintenance techniques in periodically examining and diagnosing the health of IMs which results in sporadic breakdowns of IMs. Such breakdowns sometimes force the entire production process to stop for emergency maintenance resulting in a huge loss in the company’s revenue. Hence, top management decides to switch the operational practice to real-time predictive maintenance instead. Intelligent sensors are installed on IMs to collect necessary information related to their working statuses. ML exploits the real-time information received from intelligent sensors to flag abnormalities of mechanical or electrical components of IMs before potential failures are reached. Four ML models are investigated to evaluate which one is the best, i.e. Artificial Neural Network (ANN), Particle Swarm Optimization (PSO), Gradient Boosting Tree (GBT) and Random Forest (RF). Standard performance metrics are used to compare the relative effectiveness among different ML models including Precision, Recall, Accuracy, F1-score, and AUC-ROC curve. The results reveal that PSO not only obtains the highest average weighted Accuracy but also can differentiate the statuses (Class 0 – Class 3) of the IM more correctly than other counterpart models
Parity-Time Symmetric Capacitive Wireless Power Transfer with Extended Transfer Distance
Get PDFDespite increasing popularity of capacitive wireless power transfer as a complementary technique to its inductive counterpart, the capacitive system entails a major performance bottleneck in terms of robustness of power transfer level over separating distance due to inherently low nature of electric couplings as compared to magnetic fields. This work develops an enhanced capacitive wireless power transfer system by means of incorporating the parity-time symmetry, with the capability to maintain transferred power over a significantly extended distance. General theoretical analysis is derived for parity-time symmetric capacitive power transfer based on both series and parallel coupled resonators. A practical parity-time symmetric capacitive system with a 10-W power delivery was designed and simulated. Extensive simulation using practical components indicates more than twenty-fold increase in the transfer distance than its conventional non-parity-time-symmetric capacitive counterpart, with an efficiency over 90%
Recent Advances and Applications of Fractional-Order Neural Networks
Get PDFThis paper focuses on the growth, development, and future of various forms of fractional-order neural networks. Multiple advances in structure, learning algorithms, and methods have been critically investigated and summarized. This also includes the recent trends in the dynamics of various fractional-order neural networks. The multiple forms of fractional-order neural networks considered in this study are Hopfield, cellular, memristive, complex, and quaternion-valued based networks. Further, the application of fractional-order neural networks in various computational fields such as system identification, control, optimization, and stability have been critically analyzed and discussed
Reducing Complexity on Coding Unit Partitioning in Video Coding: A Review
Get PDFIn this article, we present a survey on the low complexity video coding on a coding unit (CU) partitioning with the aim for researchers to understand the foundation of video coding and fast CU partition algorithms. Firstly, we introduce video coding technologies by explaining the trending standards and reference models. They are High Efficiency Video Coding (HEVC), Joint Exploration Test Model (JEM), and VVC, which introduce novel quadtree (QT), quadtree plus binary tree (QTBT), quadtree plus multi-type tree (QTMT) block partitioning with expensive computation complexity, respectively. Secondly, we present a comprehensive explanation of the time-consuming CU partitioning, especially for researchers who are not familiar with CU partitioning. The newer the video coding standard, the more flexible partition structures and the higher the computational complexity. Then, we provide a deep and comprehensive survey of recent and state-of-the-art researches. Finally, we include a discussion section about the advantages and disadvantage of heuristic based and learning based approaches for the readers to explore quickly the performance of the existing algorithms and their limitations. To our knowledge, it is the first comprehensive survey to provide sufficient information about fast CU partitioning on HEVC, JEM, and VVC
Performance Investigation of the Reverse Anoxic/Anaerobic/Oxic Microbial Fuel Cell
Get PDFA reverse anaerobic/anoxic/aerobic (A2O) process is recognized as a developed biological nutrient removal process for wastewater treatment. A few researchers recently integrated a microbial fuel cell (MFC) into an A2O process to generate electricity during wastewater treatment. However, no published studies show the outcome of combining the MFC with the reverse A2O process. The performance of a reverse A2O-MFC during the treatment of raw duck pond water was investigated in this study. For suitable electrode placement, nine patterns of anode and cathode location (CH01-CH09) were also investigated. As a result, 60-79%, 14-52%, 57-82%, and 50-82% of phosphates, nitrates, total ammonia nitrogen, and COD were removed, respectively. Lineweaver-Burk plots could be used to estimate the system's phosphate removal rates. The highest electrical energy was observed at CH05 (162.5 Wh) in the first period of the treatment operation and at CH02 (710.3 Wh) in the second period. The electrode placement patterns of CH05, where the anode and cathode were installed in an anaerobic tank and an oxic tank, and CH02, where the anode and cathode were installed in an anoxic tank and an anaerobic tank, were recommended for the reverse A2O-MFC with a 35-cm electrode distance
Damage Index Seismic Assessment Methodologies of URM Buildings: A State-of-the-Art Review
Get PDFThis paper is written to review the previous studies of developing Damage Indices (DI) for Unreinforced Masonry (URM) Buildings. DI was designed to provide a critical indicator of damage states (DS), seismic vulnerability, and structural occupancy of buildings. DI approaches with simplified assessment methods to predict seismic vulnerability of URM structures are presented in this review, with the pros and cons of each assessment method are highlighted to propose an ideal methodology in using DI assessment. Thus, this paper is intended to provide a comprehensive information related to the state-of-the-art of DI methodology that can be used to seismically assess of URM buildings
Investigation of Fineness and Calcium-Oxide Content in Fly Ash from ASEAN Region on Properties and Durability of Cement–Fly Ash System
Get PDFFly ash is a ubiquitously used pozzolan in cementitious material. Its technical knowledge has been widely studied for several decades and seems very well-established. However, a practical challenge currently exists. Different fly ash, even in different batches produced from similar power plant, has a wide variation of properties. To better control the wide variation of properties, this study aims to assess the effects of cementitious mixtures containing different fly ash properties (degree of fineness and CaO content) on heat release, flow, compressive strength, chloride ion penetration resistance, and carbonation resistance. Results from statistical analysis of 270 tested data of fly ash in various ASEAN countries indicate that the fineness of fly ash particle influences on the compressive strength, chloride ion penetration resistance, and carbonation resistance. Whereas, the CaO content of fly ash only statistically impacts on the compressive strength, but not on the chloride ion penetration resistance and carbonation resistance. To reduce the current practical challenge of the wide variation of cement–fly ash composite properties, their durability properties can be improved by adding smaller fly ash particle in cement system. The control of fly ash production by delivering its optimal degree of fineness is more important than selecting the optimal CaO content of fly ash. The study offers a deep technical value differentiating between effects of its fineness and CaO content such that the fly ash producers and consumers can realize and offer the optimized fly ash for good product quality