Journal of Engineering and Technological Sciences
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Corrosion Behavior of Steel 37 under Dynamic Conditions in 0.1 N H2SO4
Full text linkAn aggressive environment has a substantial effect on the progression of corrosion on metal surfaces and alloys. This study investigated the effect of one of the parameters that affect the corrosion process, the stirring rate, on the behavior of Steel 37 in 0.1 N of sulfuric acid. The main method used in this study is an electrochemical method (using a potentiostat at a scan rate of 3 MV.sec-1), applied at three different temperatures (25, 30, and ˚C). To evaluate the parameters of corrosion in this study, the Tafel extrapolation method was used. At a constant stirring rate, the corrosion current density was found to be increased with increasing temperature at a constant stirring rate. In addition, the corrosion rate increased with increasing stirring rate at a constant temperature due to the rise of the diffusion coefficient of oxygen. The Levich equation was used to calculate the limiting current densities, as well as the mass transfer coefficient (Km) and the Sherwood number (Sh). The Km values were calculated and it was found that the mass transfer coefficient was greater at higher temperatures and stirring rates. The results also revealed that the smallest values of Sh (2.575, 3.897) occurred at 30 °C at two stirring rates (200 and 400 rpm)
Study of Aquatic Sedimentation Using Electromagnetic Modeling in Flood Hazard Mitigation Scheme
Full text linkThe accumulation of sediment in aquatic environments can lead to an increase in flood risk due to raised floodplains and water levels. Electromagnetic modeling techniques, such as Time Domain Electromagnetic (TDEM) resistivity or lithological conductivity contrast, can be utilized to detect changes in the subsurface. In this study, we investigated the use of TDEM in flood hazard mitigation schemes by developing a 1-D forward modeling program for the central loop configuration in an aquatic environment using the Adaptive Born Forward Mapping (ABFM) method. The program was tested in various environmental conditions, i.e., freshwater, brackish water, and saltwater, to determine its response. The objective is to prevent natural disasters, particularly flooding caused by sedimentation. The TDEM models can generate images of sediment thickness, providing a sensitive response in saltwater environments and enabling the detection of changes in depth compared to other aquatic environments. Overall, this study demonstrated the potential of TDEM as a valuable tool in flood hazard mitigation schemes
Modification of Culvert Design on Discharge Channel: A Case Study in Indonesian Coal-Fired Power Plant
Full text linkThe construction of a new CFPP in Indonesia, which was located next to three existing power plants and utilized an existing discharge channel, faced the problem of insufficient capacity of the existing discharge channel to deliver water to four power plants. The problem occurred not only because of the overcapacity of the cooling water flow proposed by the new CFPP but also because of the small size of the culvert located in the discharge channel. This paper discusses several methods to overcome this problem by enlarging the culvert area or by removing the culvert from the channel and replacing it with a bridge. A hydraulic study was investigated using the HEC-RAS software by utilizing inputs obtained from the existing channel geometry and flow measurement data. It was found that additional culverts on both sides with a size of 2 m x 4 m and 3 m x 1 m could reduce the water level by 1.12 m and 0.39 m, respectively. Meanwhile, removing the culvert provided a significant water level reduction of 1.39 m. Enlarging the culvert was chosen as the solution to the discharge channel capacity issue since removing the culvert would require temporarily closing the channel during construction and stopping the operation of the existing power plant
Pixel Value Graphical Password Scheme: Analysis on Time Complexity performance of Clustering Algorithm for Passpix Segmentation
Full text linkPasspix is a key element in pixel value access control, containing a pixel value extracted from a digital image that users input to authenticate their username. However, it is unclear whether cloud storage settings apply compression to prevent deficiencies that would alter the file's 8-bit attribution and pixel value, causing user authentication failure. This study aims to determine the fastest clustering algorithm for faulty Passpix similarity classification, using a dataset of 1,000 objects. The source code for the K-Means, ISODATA, and K-Harmonic Mean scripts was loaded into a clustering experiment prototype compiled as Clustering.exe. The results demonstrate that the number of clusters affects the time taken to complete the clustering process, with the 20-cluster setting taking longer than the 10-cluster setting. The K-Harmonic Mean algorithm was the fastest, while K-Means performed moderately and ISODATA was the slowest of the three clustering algorithms. The results also indicate that the number of iterations did not affect the time taken to complete the clustering process. These findings provide a basis for future studies to increase the number of clusters for better accuracy
Al-Cu Composite’s Springback in Micro Deep Drawing
Full text linkWith the recent technological trend of miniaturization in manufacturing industries, the rise of micro forming operations such as micro deep drawing (MDD) is inevitable. On the other hand, the need of more advanced materials is essential to accommodate various applications. However, a major problem are size effects that make micro scale operations challenging. One of the most important behaviors affected by size effects is the springback phenomenon, which is the tendency of a deformed material to go back to its original shape. Springback can affect dimensional accuracy, which is very important in micro products. Thus, this paper investigated the springback behavior of Al-Cu composite in MDD operations. Micro cups were fabricated from blank sheet specimens using an MDD apparatus with variation of annealing holding time. The springback values were measured and compared to each other. The results showed that different grain sizes lead to variation in the amount of springback. However, unlike in single-element materials, the amount of springback in Al-Cu composite is not only related to the thickness to grain size (t/d) ratio. Another factor, i.e., the existence of an interfacial region between layers, alters the mechanical behavior of the composite
Thermodynamic Study on Decarbonization of Combined Cycle Power Plant
Full text linkIntegrating hydrogen firing and a carbon capture plant (CCP) into a natural gas combined cycle (NGCC) power plant is a promising strategy for reducing CO2. In this study, process simulation in Aspen PLUS of hydrogen co-firing in a 40 MW turbine gas combined cycle power plant was done at an identical gas turbine inlet temperature from 0%.cal to 30%.cal. The evaluated cases were hydrogen co-firing with CCP (H2 Co-firing + CCP) and hydrogen co-firing without CCP (H2 Co-firing). The results showed a 6% CO2 emission reduction per 5% increase in hydrogen, albeit with increased NOx emissions. H2 Co-firing experienced a decrease in net power with rising hydrogen co-firing, while H2 Co-firing + CCP saw an increase but remained below Case 2 due to the energy penalty from the carbon capture plant. The capital cost of H2 Co-firing + CCP exceeds that of H2 Co-firing due to CCP usage, impacting gross revenue. The sensitivity analysis indicated that the cost of hydrogen has higher sensitivity compared to the cost of CCP. Lowering hydrogen prices is recommended to effectively reduce CO2 emissions in NGCC
Evaluation of Drainage System of Light Rapid Transport (LRT) Depo – Kelapa Gading – Jakarta City
Full text linkLRT Depo is a vital infrastructure in the operation of Jakarta’s LRT system. The LRT Depo is located in the Kelapa Gading area. Kelapa Gading is an inundation-prone area in Jakarta. Hence a drainage system should be prepared to manage surface runoff in the area to avoid additional runoff to the surrounding drainage system. In order to reduce runoff in Jakarta Special Province, the Governor of Jakarta has imposed a regulation on surface runoff management for every developed area. The runoff control measures, promoted in the regulation to be applied, are in the form of infiltration wells and storage ponds. The principle of reducing peak discharge by a possible storage system for LRT Depo was designed and applied to comply with regional regulations on rainwater control. The drainage system, initially based on the regulations, was also modeled in the Storm Water Management Modelling software (SWMM). This study evaluated the drainage system by elaborating the reduction of the peak discharge based on the simulation. A reduction of peak discharge was observed in the modeling results. The proposed runoff control at LRT Depo Kelapa Gading is a proper design of infrastructure development for a flood prone area
Bandwidth and Gain Enhancement of Microstrip Leaky-Wave Antennas with Slot and Defected Ground Structure
Full text linkThis paper discusses the design, simulation, and realization of a leaky-wave microstrip antenna with multiple slots and defected ground structure (DGS). The leaky-wave microstrip antenna with multiple slots and DGS was designed to operate at 5.925-6,425 GHz for wireless local area network applications (WLANs), with a gain of ≥4dBi. The antenna uses FR-4 epoxy as the substrate with a dielectric constant of 4.6 and a thickness of 1.6 mm. The leaky-wave microstrip antenna has dimensions of 45.1 mm × 24.8 mm × 1.6 mm, while the leaky-wave microstrip antenna with multiple slots and DGS has dimensions of 40.6 mm × 25 mm × 1.6 mm. The simulation results showed that adding multiple slots and DGS to the leaky-wave microstrip antenna increased the bandwidth from 280 MHz (5.859–6.139 GHz) to 691 MHz (5.854–6.545 GHz) while the gain increased from 4.47 to 5.04 dBi. Meanwhile, the measurement results showed that the bandwidth parameter increased from 273 MHz (5.877–6.150 GHz) to 684 MHz (5.845–6.529 GHz) and the gain parameter from 4.53 to 5.06 dBi at 6 GHz
Numerical Solution of nth Order DAEM for Kinetic Study of Lignocellulosic Biomass Pyrolysis
Full text linkThe aim of the present study was to explore the most optimal configuration to numerically solve Distributed Activation Energy Models (DAEMs). DAEMs are useful in obtaining the kinetic parameters in non-isothermal kinetic studies using a thermogravimetry analyzer (TGA). Compared to other kinetic models, DAEMs provide an additional kinetic parameter that quantifies the extent of the reaction (σ) for each reaction’s mean activation energy (E ̅). Although DAEMs are efficacious in kinetic studies, solving DAEMs numerically is challenging. The DAEM equation includes double integration with respect to activation energy and temperature, which involves various numerical discretizations. Previously, many researchers utilized a DAEM to explicate complex reactions such as lignocellulosic biomass pyrolysis. However, most of them have yet to propose a numerical approach to solve DAEMs. Therefore, by exploring multiple numerical calculation configurations, here we present a general structure to numerically solve nth order and first-order DAEMs. The exploration includes determining the optimal integration limit of activation energy and the discretization of activation energy and temperature integration. From the investigation, we came up with a configuration that limits the integration of activation energy from E ̅-3σ to E ̅+3σ. Meanwhile, the number of integration points for temperature and activation energy must be 51 and 21, respectively. By using this configuration, DAEM can be utilized optimally in kinetic studies