Journal of Engineering and Technological Sciences
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    869 research outputs found

    Reducing Numerical Dispersion with High-Order Finite Difference to Increase Seismic Wave Energy: -

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    The numerical dispersion of 2D acoustic wave modeling has become an interesting subject in wave modeling in producing better subsurface images. Numerical dispersion is often caused by error accumulation with increased grid size in wave modeling. Wave modeling with high-order finite differences was carried out to reduce the numerical error. This study focused on variations in the numerical order to suppress the dispersion due to numerical errors. The wave equation used in modeling was discretized to higher orders for the spatial term, while the time term was discretized up to the second order, with every layer unabsorbed. The results showed that high-order FD was effective in reducing numerical dispersion. Thus, subsurface layers could be distinguished and observed clearly. However, from the modeling results, the wave energy decreased with increasing distance, so the layer interfaces were unclear. To increase the wave energy, we propose a new source in modeling. Furthermore, to reduce the computational time we propose a proportional grid after numerical dispersion has disappeared. This method can effectively increase the energy of reflected and transmitted waves at a certain depth. The results also showed that the computational time of high-order FD is relatively low, so this method can be used in solving dispersion problems

    Effect of Sonication Frequency and Power Intensity on the Disruption of Algal Cells: Under Vacuum and Non-Vacuum Conditions

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    The presence of algae caused by anthropogenic eutrophication in water has become a severe environmental issue. Various treatment options for algae removal have been developed, such as filtration, coagulation, sedimentation, flotation, algicides, ozone, and photolysis. However, these technologies are complex, expensive, consume considerable amounts of various chemicals, and may cause further pollution (i.e., by-product formation). Ultrasonic exposure is an alternative method for removing algae from water that is environmentally friendly (i.e., no addition of chemicals) and almost unaffected by any turbidity in the water. In this study, process optimization of ultrasonication (e.g., by adjusting frequency, power intensity, and exposure time) for the removal of alga was tested under vacuum and non-vacuum conditions. Experiments were conducted on a batch of algae solution in a clear glass tube ultrasonicated by a 20 kHz transducer for 180 minutes. The tube was depressurized up to -67 N/m2 in a depressurizing chamber. The data was collected at transducer depths of 0.06, 0.13, and 0.19 m. It was concluded that the optimum condition (i.e., 92% algal cell disruption) was achieved when the power intensity was 7 kWh/m3, under vacuum conditions, at a frequency of 20 kHz and 180 minutes of exposure time. Higher power intensity gave higher energy for cell disruption, moreover by depressurizing the air above the algae solution, the lysis effect for algae reduction increased from 20% to 70% compared to the non-depressurized system due to higher cavitation bubble production. In addition, the depth of the transducer was another factor that could increase the lysis of the algae water. Therefore, this technology has future potential application for algae removal from water

    The Material Science Behind Repetitive Hammering, Solution Annealing, and Tempering on Hadfield Steel

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    The Hadfield steel used in this study contained 11 to 14% Mn and 1.1 to 1.4% C. Hadfield steel that underwent heat treatment showed insignificant differences in microstructure and hardness. On the other hand, Hadfield steel that was subjected to heat treatment combined with repetitive hammering exhibited changes in microstructure, as indicated by the presence of more and denser slip lines in accordance with an increased amount of deformation. The hardness value of the Hadfield steel also significantly increased. The slip lines discovered in the Hadfield steel that underwent solution annealing and tempering followed by repetitive hammering increased in number and appeared more compact than in the Hadfield steel without tempering. Additionally, the hardness value of the Hadfield steel with tempering was higher than that of the Hadfield steel without tempering. The strain values and thickness reduction results showed that the Hadfield steel subjected to tempering had higher strain and thickness reduction than the Hadfield steel without tempering. Higher strain and thickness reduction leads to higher hardness

    Microplastic Removal from Road Stormwater Runoff using Lab-scale Bioretention Cell

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    Microplastic removal from stormwater runoff from roads is necessary to reduce the effect of microplastic pollution in water bodies. Bioretention is a potential technology to remove microplastics in stormwater runoff from roads. A lab-scale experiment was conducted to determine the efficiency, effect on vegetation and discharge variation, and the kinetics of microplastic removal from stormwater runoff from roads using a bioretention cell. The experiment was done using an artificial sample based on visual characterization of stormwater runoff from highways, commercial, and residential roads. The vegetations that were examined were Vetivera sp. and Hibiscus sp. The operational discharge was varied based on rainfall intensity categories. The result showed that the removal efficiency was in the range of 92.4 to 99.3% with a mean of 97.2%. Statistical analysis (ฮฑ = 5%) showed that variation in vegetation and discharge had no significant effect on microplastic removal using bioretention. The first-order kinetic analysis showed that the kinetic removal constant of the bioretention with Vetivera sp., bioretention with Hibiscus sp., and bioretention without vegetation was 0.0356, 0.034, and 0.0327, respectively. These results indicate that bioretention with Hibiscus sp. removed more microplastics at greater depths than with Vetivera sp

    Thermodynamic Study on Decarbonization of Combined Cycle Power Plant

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    Integrating 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 to 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

    Influence of Opening and Boundary Conditions on the Behavior of Concrete Hollow Block Walls: Experimental Results

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    The assembled pattern of concrete hollow building blocks contributes to the wall structureโ€™s durability. This paper presents experimental research on the behavior of concrete hollow block walls. The experimental work included testing four concrete hollow block wall panels with different opening sizes. Constant vertical axial load was applied on top of the wall panels until failure, characterized by boundary conditions. The results showed that the presence of openings reduced the strength of the wall panels; it was possible to observe these differences since the opening area was between 20 and 40% of the gross wall panel area. It was also observed that while the opening percentage had a significant impact on the strength of the wall, the boundary conditions had a less substantial impact on the overall wall response. A high localized concentration of stress was observed at the top corners of the wall panels and a high stress concentration was also observed along the vertical sides of the openings. Variation in the number and the shape of the openings often changed the failure mechanism in the wall panels, even when the percentage area of the opening remained constant. The wall panels A1-B2 reached peak stress levels at 0.019 MPa, 0.036 MPa, 0.056 MPa, and 0.030 MPa. The equivalent peak strains were 0.018, 0.011, 0.012, and 0.010 respectively. This research established significant data and is expected to help in the design and analysis of axially loaded unreinforced masonry walls with openings

    The Risk of Failure Assessment in Bina Marga Standard Designed Prestressed Concrete Girder Bridges under B-WIM Load Measurement

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    The use of precast prestressed concrete girder bridges in Indonesia has been increasing rapidly due to their high quality, reliability, and faster construction on site. The girder components are typically designed for a specific bridge span and can be prefabricated. The Directorate General of Highways of the Ministry of PUPR (Bina Marga) has released a standard design for prestressed concrete girder bridges with a typical span of up to 40 m. This design is based on the bridge loading standard SNI 1725 2016, which determines the live traffic load through consensus due to limited data on actual traffic load measurement results. However, the Ministry of PUPR has been implementing actual traffic load measurements using weigh-in-motion (WIM) technology to directly measure the load of passing vehicles. In this study, a risk assessment of the failure risk of a standard Bina Marga bridge with a 40-m span prestressed concrete girder type was conducted based on B-WIM load measurements. The results of this assessment indicate that the standard Bina Marga bridge has a failure risk of 1.48 x 10-4, which is smaller than the acceptable risk of failure according to the AASHTO LRFD Bridge Design Specification as referenced in SNI 1725 2016

    Evaluation of Drainage System of Light Rapid Transport (LRT) Depo โ€“ Kelapa Gading โ€“ Jakarta City

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    LRT Depo is a vital infrastructure in the operation of Jakartaโ€™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

    Advancements, Challenges, and Future Directions in Rainfall-Induced Landslide Prediction: A Comprehensive Review

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    Rainfall-induced landslides threaten lives and properties globally. To address this, researchers have developed various methods and models that forecast the likelihood and behavior of rainfall-induced landslides. These methodologies and models can be broadly classified into three categories: empirical, physical-based, and machine-learning approaches. However, these methods have limitations in terms of data availability, accuracy, and applicability. This paper reviews the current state-of-the-art of rainfall-induced landslide prediction methods, focusing on the methods, models, and challenges involved. The novelty of this study lies in its comprehensive analysis of existing prediction techniques and the identification of their limitations. By synthesizing a vast body of research, it highlights emerging trends and advancements, providing a holistic perspective on the subject matter. The analysis points out that future research opportunities lie in interdisciplinary collaborations, advanced data integration, remote sensing, climate change impact analysis, numerical modeling, real-time monitoring, and machine learning improvements. In conclusion, the prediction of rainfall-induced landslides is a complex and multifaceted challenge, and no single approach is universally superior. Integrating different methods and leveraging emerging technologies offer the best way forward for improving accuracy and reliability in landslide prediction, ultimately enhancing our ability to manage and mitigate this geohazard

    Investigation on Neutronic Parameters of the KLT-40S Reactor Core with U3Si2-FeCrAl using SCALE Code

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    From a safety point of view, the fuel-cladding of the current design of the KLT-40S reactor still carries a potential risk in the event of a loss-of-coolant accident (LOCA) allowing the formation of hydrogen gas. The concept of accident tolerant fuels (ATF) offers a variety of new safer fuel-cladding materials, one of which is U3Si2-FeCrAl, a potential fuel-cladding combination according to various research sources. In this research, a study of neutronic parameters (1) cycle length, (2) reactivity feedback coefficient, and (3) reactor proliferation resistance was performed with ATF material U3Si2-FeCrAl as fuel-cladding in the KLT-40S reactor core. Modeling and simulation of the ATF-fueled KLT-40S reactor core were performed using KENO-VI and TRITON modules from SCALE code. The results showed that replacement of the fuel-cladding material with the ATF material in the KLT-40S reactor resulted in a shorter cycle length, and the enrichment required to reproduce the original cycle length was above the safeguard limit. The fuel temperature, moderator temperature, and void reactivity coefficient were negative, although not as negative as the original ones. The spent fuel produced at the end of the cycle had good proliferation resistance, although not as good as the original one


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    Journal of Engineering and Technological Sciences
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