Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
Not a member yet
1223 research outputs found
Sort by
Flood Risk Index for Land-Use Changes: Case Study of Pakpanang River Basin
Get PDFFlood Risk Index (FRI) is the multi-criteria linked with the factors of vulnerability; exposure, susceptibility, and resilience. In order to establish local FRI, crucial local information have to be accumulated. However, under the limitation of land-use data, particular techniques were applied in this study. CA Markov model was used to analyze the past missing land-use data and, also forecast the future land-use of Pakpanang river basin under conditions of plan and without plan. The ratio changes of forest, agriculture, wetland and water, and urban areas were considered. Then, the result of LULC spatial-temporal changes was then applied to Hec-HMS and Hec-Ras , with Arc GIS extension of Hec-GeoHMS and Hec-GeoRas software, in order to evaluate the flood hydrographs and flood severity in three municipalities corresponding to 100-year return period rainfall. Afterward, the FRI of Pakpanang, Chianyai, and Hua-sai, which ranges from 0 to 1, were evaluated by using the modified FRI equations. It was found that sensitivity analysis in the area of forest on flood depth and inundation areas is incoherent. Nevertheless, without land-use planning, the changes in these three cities cause higher flood risk, where Chianyai is the riskiest as the FRIE is 0.58. Further consideration of FRIE and FRIP proportion that reveals the FRI deviation indicates that to reduce flood risk, Chianyai would need the most resources and highest effort comparison to Pakpanang and Hua-sai
Investigation of Parameters That Affect the Acquired Near Infrared Diffuse Reflected Signals in Non-Destructive Soluble Solids Content Prediction
Get PDFNear infrared spectroscopy is a susceptible technique which can be affected by various factors including the surface of samples. According to the Lambertian reflection, the uneven and matte surface of fruits will provide Lambertian light or diffuse reflectance where the light enters the sample tissues and that uniformly reflects out in all orientations. Bunch of researches were carried out using near infrared diffuse reflection mode in non-destructive soluble solids content (SSC) prediction whereas fewer of them studying about the geometrical effects of uneven surface of samples. Thus, this study aims to investigate the parameters that affect the near infrared diffuse reflection signals in non-destructive SSC prediction using intact pineapples. The relationship among the reflectance intensity, measurement positions, and the SSC value was studied. Next, three independent artificial neural networks were separately trained to investigate the geometrical effects on three different measurement positions. Results show that the concave surface of top and bottom parts of pineapples would affect the reflectance of light and consequently deteriorate the predictive model performance. The predictive model of middle part of pineapples achieved the best performance, i.e. root mean square error of prediction (RMSEP) and correlation coefficient of prediction (Rp) of 1.2104 °Brix and 0.7301 respectively
Sustainability Indicators to Assess Infrastructure Projects: Sector Disclosure to Interlock with the Global Reporting Initiative
Get PDFInfrastructure projects have great potential to impact the sustainability of cities due to typically being large-sized projects and having a high level of intervention. Thus, evaluating the sustainability of these projects through sustainability reports is highly relevant, mainly regarding their impacts on the environment, public health, and the local economy. The Global Reporting Initiative (GRI) is the most widespread and internationally accepted Sustainability report tool. However, the GRI does not have an infrastructure sector disclosure. This research addresses this gap by providing a sustainability assessment instrument for infrastructure projects that interlocks with the Global Reporting Initiative (GRI). An extensive and detailed literature review was conducted, identifying 97 potential indicators to measure the sustainability of infrastructure projects. These indicators were evaluated following a top-down approach, conducting a survey of professionals experienced in the relevant field using Lawshe's content validity ratio. The results showed that 42 indicators were validated as essential, with 21 of them, not specifically related to infrastructure projects, already covered by the standard disclosure of the GRI. This assessment enabled the proposal of a sector disclosure formed by 21 new indicators related to the environmental, economic, and social dimensions. This study closes a gap in the evaluation of the sustainability of infrastructure projects and contributes to the discussion about sustainability indicators in infrastructure projects
Oblique Decision Tree Algorithm with Minority Condensation for Class Imbalanced Problem
Get PDFIn recent years, a significant issue in classification is to handle a dataset containing imbalanced number of instances in each class. Classifier modification is one of the well-known techniques to deal with this particular issue. In this paper, the effective classification model based on an oblique decision tree is enhanced to work with the imbalanced datasets that is called oblique minority condensed decision tree (OMCT). Initially, it selects the best axis-parallel hyperplane based on decision tree algorithm using the minority entropy of instances within the minority inner fence selection. Then it perturbs this hyperplane along each axis to improve its minority entropy. Finally, it stochastically perturbs this hyperplane to escape the local solution. From the experimental results, OMCT significantly outperforms 6 state-of-the-art decision tree algorithms that are CART, C4.5, OC1, AE, DCSM and ME on 18 real-world datasets from UCI in term of precision, recall and F1 score. Moreover, the size of decision tree from OMCT is significantly smaller than others
Frame Size Analysis of Optimum Dynamic Tree in RFID Systems
Get PDFIn RFID (Radio Frequency Identification) system, an anti-collision algorithm plays a prominent role in the tag identification process in order to reduce the tag identification delay and enhance the RFID system efficiency. In this work, we present a theoretical analysis of optimal frame size assignment for maximizing the system efficiency of a tree-based anti-collision algorithm, called optimum dynamic tree (ODT) algorithm, for RFID tag identification process. Our analysis indicates that the appropriate frame size for a given number of competing tags should not be set to the same value as the number of tags, which is commonly adopted in the literature. Instead, the frame size should be smaller roughly by a factor of 0.871 to maximize system efficiency. The closed-form for calculating system efficiency is derived and the derived simulation results are in a good agreement with the theoretical one. The exact appropriate frame sizes for the number of tags ranging from 2 to 100 are tabulated and compare the tag-identification time of conventional binary tree and ODT algorithms by using the international standard ISO 18000-6B
Virtual Oscillator Control of Multiple Solar PV Inverters for Microgrid Applications
Get PDFThis paper proposes the inverter control strategy for multiple solar PV generation sources based on the two-stage converters with a combination of the modified virtual oscillator control (VOC) and the cascaded sliding mode control (SMC). With this proposed control strategy, the load power-sharing in proportion to the inverter rating is guaranteed when the solar PV output satisfies the power-sharing requirement. On the other hand, the control algorithm autonomously forces the solar PV to operate at the maximum power point if the solar PV output is lower than the power-sharing requirement. Various operating scenarios have been simulated to appreciate the effectiveness of the proposed control scheme for ensuring the load-power sharing and maintaining the voltage and frequency stability of the islanded microgrid containing a 100% solar PV generation
Investigation of the Electronic Thermal Transport in Thin Silicon Films with Varying Electric Field and Doping Concentration
Get PDFScatterings of electrons by ionized impurities in semiconductors have been comprehensively explored by various methods. However, the electron-impurity scattering was not investigated under an electric field at thin silicon (Si) films. The effects of electric field on electronic thermal conductivity in thin Si films at different doping concentration at room temperature are investigated by using an analytical model based on the Boltzmann transport equation with the relaxation time approximation. As expected, the electronic thermal conductivity increases as the external electric field increases. More importantly, we show that the scattering between carrier and impurity is a dominant scattering mechanism in Si films at high doping level such as above 1018 cm-3 under the influence of an electric field. The effect of the electron-phonon interaction on the electronic thermal conductivity of silicon can be neglected because electron mean free path is significantly reduced due to the impurity scattering and the effect of electric field. Since there is no experimental attempt to measure the electron and the phonon thermal conductivities with the electric field applied, the result is given of some simplified concepts that will contribute to a better understanding of electron transport fundamentals
Degradation of 2,4-Dichlorophenol in Aqueous Solution by Ozonation in the Presence of Iron Oxide Compound in Bubble Column Reactor
Get PDFChlorophenols are a group of chemical substances given special attention by experts and researchers of industrial wastewater due to their high toxicity and low biodegradability. The degradation of these compounds, often used in studies is 2,4- Dichlorophenol (2,4-DCP), either use conventional processing methods or contemporary approaches such as catalytic ozonation and AOPs (Advanced Oxidation Processes). The laboratory-scale 2,4-DCP degradation technique in this study was carried out in a multi- injection bubble column, with very satisfactory processing results. This is mainly due to the ability of hydroxyl radicals to decompose almost all 2,4-DCP in wastewater as well as not giving out a dangerous product. Specifically, the chlorophenol waste used here is a synthetic wastewater or dilute 2,4-DCP solution focused on investigating the effect of air flow rate, wastewater flow rate, and the amount of iron oxide (FeO and / or Fe2O3) involved. This bench scale processing of 2,4-DCP degradation is a semi-continuous, with an initial concentration of 2,4-DCP of 50 ppm and 60 minutes of ozonation time. In this study, the use of FeO and/or Fe2O3 catalysts does not significantly affect the degradation efficiency of 2,4-DCP. With the non-catalytic ozonation technique, the highest percentage of phenolic and COD degradation obtained was 99.83% and 84.31% at an air flow rate of 12 L / min and a wastewater flow rate of 495 mL / min. For catalytic ozonation, the highest phenolic and COD degradation under the same operating conditions was 99.64% and 86.44%
Modeling of Partial Hydrogenation of Polyunsaturated Fatty Acid Methyl Esters in a Trickle Bed Reactor
Get PDFPartial hydrogenation of polyunsaturated fatty acid methyl esters in a trickle-bed reactor was modeled and simulated in this study with the objectives being to investigate the performance of the reactor, to predict the effect of process parameters on the reactor performance, and to observe the radial heat transfer in the reactor. The reactor possessed the aspect ratio of 100 and was packed with spherical catalyst particles. A steady-state heterogeneous model was applied. The gas and liquid phases were modeled in two-dimensional axisymmetric model, which consist of mass balance for each phase, energy balance and momentum balance. The momentum balance was based on the Darcy equation for two fluid phases passing through porous media. Mixing in both fluid phases is also described by dispersion coefficients. The three-dimensional solid phase model considered diffusive transport in the catalyst pores and surface reactions. Methyl linoleate was considered as polyunsaturated fatty acid methyl ester representative, and cis-methyl oleate, trans-methyl oleate and methyl stearate were as the hydrogenated fatty acid methyl esters. The simulation results for the inlet temperature of 433 K and the reactor pressure of 611 kPa with the gas flowrate being 43 times higher than the liquid one shows that the process reached 78.22% methyl linoleate conversion. The concentrations of cis-methyl oleate, trans-methyl oleate and methyl stearate at the reactor outlet are 16.2 mol/m3, 17.4 mol/m3 dan 16.6 mol/m3, respectively. The total methyl oleate produced is about twice that of methyl stearate, and its selectivity is about 53%
Prototype of Automated Shading Device: Preliminary Development
Get PDFLocated in the equator zone, Indonesia receives intense solar radiation throughout the day with the average daily solar radiation around 4 kWh/m2. Thus, shading devices particularly movable shading device play an important role to reduce the effects of solar radiation. This study aims to develop external automated shading devices horizontally, the results of the performance test for mechanical and control systems only were reported in this paper. These systems consist of four primary components; window frames and panes, mechanical system, sensors and acquisition data system, and control system. Window frame used Manglid (Manglieta glauca) wood while the windowpanes were developed from corrugated plastic sheet. As a mechanical system, the DC motor stepper with a torque value of 3.6Nm was used as an actuator device to change the rotation angles of the panes. Instead of solar radiation sensor, the TSL2561-illuminance sensor was applied due to its affordability. It was integrated to a microcontroller device (Arduino Mega 2560) and the Arduino IDE was employed to input its algorithms. The control system contained a set of algorithms that enabling the windowpanes to move according to the illuminance received by the sensor and the sun path data input to the program. The two respective performance tests were conducted in the laboratory by illuminating the sensor using an artificial light source and installed the shading device on the test house under actual condition. The results demonstrated that the mechanical and control systems worked properly, and they were synchronized. The accuracy of the sensor was about 53.2–85.8 and the response time for the actuator was less than 3 seconds