Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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A New Incremental Decision Tree Learning for Cyber Security based on ILDA and Mahalanobis Distance
Get PDFA cyber-attack detection is currently essential for computer network protection. The fundamentals of protection are to detect cyber-attack effectively with the ability to combat it in various ways and with constant data learning such as internet traffic. With these functions, each cyber-attack can be memorized and protected effectively any time. This research will present procedures for a cyber-attack detection system Incremental Decision Tree Learning (IDTL) that use the principle through Incremental Linear Discriminant Analysis (ILDA) together with Mahalanobis distance for classification of the hierarchical tree by reducing data features that enhance classification of a variety of malicious data. The proposed model can learn a new incoming datum without involving the previous learned data and discard this datum after being learned. The results of the experiments revealed that the proposed method can improve classification accuracy as compare with other methods. They showed the highest accuracy when compared to other methods. If comparing with the effectiveness of each class, it was found that the proposed method can classify both intrusion datasets and other datasets efficiently
Citronella Oil Microencapsulated in Carboxymethylated Tamarind Gum and its Controlled Release
Get PDFCitronella oil is one of possible natural insect’s repellents extracted from leaves of Cymbopogon winterianus. It is used extensively as a source of perfumery chemicals such as 25% citronellal, 18% citronellol and 20% geraniol. To prolong the citronella oil release, carboxymethylated tamarind gum (CTG) was used as coating material for citronella oil encapsulation and compared to crude tamarind gum (TG), using spray drying technique. Three formulas of microcapsule were prepared at different gum to oil ratios (1.25, 1.14, and 0.87). The appearance feature of CTG microcapsule from SEM images showed a smooth surface while TG microcapsule showed many holes and crack on particle surface. It was observed that increasing the gum to oil ratio increases the retention of citronella oil in microcapsules. At 1.14 gum to oil ratio, CTG microcapsules were shown longer oil retention more than one month. The citronella oil release mechanism was analyzed by different kinetic models such as Korsmeyer-Peppas, Higuchi, and Avrami’s models. The microcapsules were found to release the citronella oi
Corrosion Resistance of Modified Heat-Treated 16Cr-4Ni Steel for Geothermal Steam Turbine Blades
Get PDFImmersion corrosion tests and electrochemical corrosion tests were carried out in the simulated geothermal water on a modified heat-treated material of 16Cr-4Ni steel, which is used for geothermal steam turbine blades. Incidentally, the purpose of the modified heat treatment is for reducing the susceptibility of stress corrosion cracking (SCC) of the steel in the geothermal fluids. For comparison, a conventional heat-treated material of the 16Cr-4Ni steel was also used in the corrosion tests. In the immersion corrosion tests up to 4,000 hours, the modified heat-treated material showed lower corrosion rates than those of the conventional heat-treated one in the test water. In the electrochemical corrosion tests, the modified heat-treated material exhibited noble and stable corrosion potential behavior. The XPS analysis results exhibited that the passive films formed on the materials were consisted mainly of Cr-oxides (CrOOH, CrO3) and Fe-oxides (FeO, Fe2O3). Furthermore, the composition ratio of Cr-oxides in the outermost surface of the passive film formed on the modified heat-treated material was higher than that on the conventional heat-treated one. It was suggested that the better corrosion resistance of the modified heat-treated 16Cr-4Ni steel was contributed to the formation of the passive film with higher compositions of Cr-oxides
Application of Heuristic Algorithms in Improving Performance of Soft Computing Models for Prediction of Min, Mean and Max Air Temperatures
Get PDFTraditionally, climate conditions has been one of the influential factors in population growth in worldwide. Hence, predicting these conditions can be an important step to improve life conditions in worldwide. In this study, application of genetic algorithm (GA) and particle swarm algorithm (PSO) were considered as alternatives to available algorithms for training artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) in order to predict air temperature. Therefore, monthly minimum, average and maximum air temperatures of Tehran-Iran station at 64-years (1951-2014) were selected as predicted time-series. Firstly, the most appropriate inputs were selected for models using sensitivity analysis. After that, long-term air temperatures (1 month, 1, 2 and 3 years ahead) were modeled. Results showed that: 1) the given algorithms had acceptable results in improving the models’ performance in modeling minimum, mean and maximum air temperatures. Also, they could improve the performance of ANN and ANFIS in most of the prediction intervals, 2) ANFIS-GA was selected as the most suitable model so that its average determination coefficient (R2), root mean square errors (RMSE) and mean absolute errors (MAE) were 0.88, 1.41 and 2.52, respectively, 3) the sensitivity analysis provided suitable results in selecting the most appropriate model inputs for forecasting the minimum, mean and maximum air temperatures in different intervals
PDMS Material Models for Anti-fouling Surfaces Using Finite Element Method
Get PDFEcofriendly anti-fouling surfaces are usually produced by lithographic techniques which will fabricate micropillar-like surfaces made of low surface energy materials such as Polydimethylsiloxane (PDMS). The purposes of this research were to investigate the most suitable Polydimethylsiloxane (PDMS) material model available in ANSYS APDL program to simulate structural behaviors of micropillars subjected to shear loading and to develop micropillar with improved lateral strength. In this research, PDMS material models were derived from experimental data from uniaxial tensile test. The accuracies of the PDMS material models, which were the Neo-Hookean, Mooney-Rivlin 3 and 5 parameters, Ogden (1, 2, 3 terms), Yeoh (1st, 2nd, 3rd order) and Arruda-Boyce material models, were evaluated and compared to experimental data from uniaxial tensile test and punch-shear test. Moreover, micropillars made of a pure PDMS and a Polyurethane Acrylate (PUA) core coated with PDMS were studied to compare their lateral strength under shear loading. We found that the most accurate material model to simulate both the uniaxial tension and shear loading was the Yeoh 3rd order material model; however, these accuracies would valid for small strain range. The lateral strength of a micropillar made of PUA core coated with PDMS was 8.67-time of the one made of pure PDMS. The thickness of the coated material was not a significant effect on lateral strength of the micropillar
Enhancement of Crossflow Ultrafiltration for the Treatment of Stabilized Oily Emulsions
Get PDFSeparation of stabilized oil droplets was conducted via crossflow ultrafiltration (UF) in a laboratory scale. A plate-and-frame membrane module was operated with two commercial organic membranes: regenerated cellulose (RC) and polyethersulfone (PES). Cutting oil was used for preparing oil-in-water emulsions. Membrane fluxes were observed under varied oil concentrations and transmembrane pressures (TMP). It was found that UF provided oil rejection more than 97% for all operational cases. The optimal operating condition was found at the oil concentration less than 1 g/L and TMP of 2−3 bar. As predicted by Hermia’s model, the dominant fouling mechanism was the cake formation upon the membrane surface. The fouled membrane was effectively regenerated by the sequential cleaning of 0.5N-SDS, 0.1N-NaOH, and 0.01N-EDTA, respectively. The cleaned membrane was acquired with 96% flux recovery (FR) and 55% resistance removal (RR). Additionally, an integration of UF and pretreatments (i.e., chemical destabilization and coalescence) could improve flux decline of the membrane, while satisfactory discharge quality was achieved
Relationship between Land Surface Temperature and Land Use in Nakhon Ratchasima City, Thailand
Get PDFThe relationship between land surface temperature (LST) and land use in Nakhon Ratchasima was studied using data gathered from three satellite images from Landsat-5 (30th January 1992), Landsat-8 (9 May 2016) and THEOS (17th February 2016). There were four categories of land use: built-up area, green area, bare land and water sources. The split-window concept was used to estimate the LST. In 1992, Nakhon Ratchasima city in Thailand comprised 47.76% built-up area, 37.45% green area, 13.19% bare land and 1.60% water sources. By 2016, the built-up area had increased by 23.04%, the green area had decreased by 16.66%, bare land had decreased by 6.81%, but water sources had increased by 0.43%. Moreover, in 1992 the mean LST was 25.43 °C for built-up areas, 24.44 °C for green areas, 24.97 °C for bare land and 24.75 °C for water sources. However, by 2016 the LSTs had increased for each category: 28.74 °C for built-up areas (+3.31 °C), 27.20 °C for green areas (+2.76 °C), 28.11 °C for bare land (+3.14 °C) and 27.72 °C for water sources (+2.97 °C). The findings indicated that the LSTs increased with the pace of urbanization and changes in land use. Linear regression analysis revealed that built-up land had a positive correlation with LST, where a 1% increase in built-up area increased its LST by 0.146594 °C
Mechanical Power to Identify Human Performance for a Lower Limb Rehabilitation Robot
Get PDFRehabilitation robots usually provide trainings with a certain training modality and activity. The patient’s performance measure such as mechanical power is also derived for those specific trainings. This article aims to demonstrate the implementation of our lower limb rehabilitation robot in sitting position for providing the training with games and to propose the derivation of the human mechanical power as a performance measure. The control algorithm for active exercise and the integration of the related software and hardware are also developed to offer proper environment for a game session. The derivation of the mechanical power of a human subject in the training is verified with active and passive cycling exercises. Three healthy subjects participate in the game sessions provided by the robot. It is found that the game sessions can provide the movement training with sufficient intensity. Moreover, the mechanical power obtained from the proposed method is able to identify the intensity of training tasks, human performance, and human attention in the training
A PDE-Based Data Reconciliation Approach for Systems with Variations of Parameters
Get PDFData reconciliation is a mathematical approach that improves the quality of measurements by calculating the reconciled data that satisfies the process constraints. The conventional data reconciliation approach relies on the process model that contains the constant parameters. In the industrial applications, however, there are always possible variations of parameters within the system. In this paper, a new data reconciliation approach based on the partial differential equation (PDE) is developed. The proposed data reconciliation approach is experimentally applied to a case study of temperature measurements for a refinery process. The PDE-based model is employed in the formulation of the optimization problem. Unlike the conventional data reconciliation approach in which the system is assumed to be lumped, the PDE-based data reconciliation approach includes in the problem formulation the variations of parameters within the system in order to describe the real system’s behaviour. The reconciled values can be computed within the computational domain so they can be used as the data for troubleshooting, equipment analysis and maintenance
Effects of Waxy Types of a Sugarcane Stalk Surface on the Spectral Characteristics of Visible-Shortwave Near Infrared Measurement
Get PDFPrecision of spectroscopic methods were frequently affected by the identity of the inhomogeneous materials, especially for direct scanning. This research aimed to investigated effects of waxy types, naturally founded on cane surface, on spectral characteristic. A portable Vis/SWNIR instrument with interactance mode across wavelength of 570-1031 nm were used for direct scanning on cane stalk. Principle component analysis (PCA) was applied to examine the differences of spectra scanned from 180 samples including 3 types of waxy type; white, black, and mixed black and white. Seven widespread pretreatments were employed to reduce the effect of waxy types. Results show that spectra of samples with each waxy type was separated in groups and SNV pretreatment gave the best results but was not able to eliminate the effect compared to the wax-removed samples. Meanwhile, the standard deviation of absorbance values, at the wavelength of 760, 904 and 970 nm of 3 samples, was used for assessing the repeatability and reproducibility. The samples with removing waxy cover provided lower the standard deviation of absorbance values of spectra than the best pretreated spectra using standard normal variate (SNV) of the samples without removing waxy cover by one to six times. Thus, the waxy material on cane surface should be removed before collect spectra