Authors:Quang Dong Pham, Van Linh Ngo, The Viet Tran, Minh Thu Trinh Pages: 220501 - 220501 Abstract: This study evaluated the use of the Asaoka and hyperbolic methods to estimate the ultimate settlement of soft ground treated by vacuum preloading combined with prefabricated vertical drains. For this aim, a large-scale physical laboratory model was constructed. The model was a reinforced-tempered glass box containing a soil mass with dimensions of 2.0 × 1.0 × 1.2 m (length × width × depth). Physical models of this scale for the same purpose are rare in the literature. The soil was taken from a typical coastal region in Dinh Vu Hai Phong, Vietnam. The surface settlement near and between the two drains was measured right after the vacuum preloading started. Important properties of the soil were tested to evaluate the effectiveness of the treatment method. The measured settlement was used in the Asaoka and hyperbolic methods to predict the potential ultimate settlement. The results showed the superiority of the vacuum consolidation approach in improving fundamental engineering properties of soft soil. Furthermore, the ultimate settlement predicted by both methods showed a good agreement with the measured value, proving that the Asaoka and hyperbolic methods are suitable for the estimation of the ultimate settlement of soft soil treated with vacuum consolidation. PubDate: 2022-09-05 DOI: 10.5614/j.eng.technol.sci.2022.54.5.1 Issue No:Vol. 54, No. 5 (2022)
Authors:Ashtar Al-Luhybi, Nuha H. Al-Jubory, Anas S. Ahmed Pages: 220502 - 220502 Abstract: This study investigated the effect of adding a type of superplasticizer (polycarboxylate ether -PCE) on the workability and mechanical properties of concrete containing recycled coarse aggregate (RCA). The effect of increasing the PCE dosage while changing the water/cement ratio on RCA strength was also studied. To accomplish these goals, three groups of concrete mixtures were prepared. The variable in these groups was the water/cement ratio (0.53, 0.57, and 0.615). In each group, the natural aggregate was replaced by two proportions of RCA (50 and 100%) and different proportions of PCE were added for each replacement ratio. The findings encourage the use of PCE in recycled concrete. It was found that the addition of PCE improves the properties of recycled concrete in terms of workability and compactness. The addition of PCE also compensates for the compressive strength that is lost due to the replacement of natural aggregate with recycled coarse aggregate. PubDate: 2022-09-05 DOI: 10.5614/j.eng.technol.sci.2022.54.5.2 Issue No:Vol. 54, No. 5 (2022)
Authors:F. Ferryanto, Andi Isra Mahyuddin, Motomu Nakashima Pages: 220503 - 220503 Abstract: This work presents the development of a markerless optical motion capture system of the front-crawl swimming stroke. The system only uses one underwater camera to record swimming motion in the sagittal plane. The participant in this experiment was a swimmer who is active in the university’s swimming club. The recorded images were then segmented to obtain silhouettes of the participant by a Gaussian Mixture Model. One of the swimming images was employed to generate a human body model that consists of 15 segments. The silhouette and model of the participant were subjected to an image matching process. The shape of the body segment was used as the feature in the image matching. The model was transformed to estimate the pose of the participant. The intraclass correlation coefficient between the results of the developed system and references were evaluated. In general, all body segments, except head and trunk, had a correlation coefficient higher than 0.95. Then, dynamics analysis by SWUM was conducted based on the joint angle acquired by the present work. The simulation implied that the developed system was suitable for daily training of athletes and coaches due to its simplicity and accuracy. PubDate: 2022-09-05 DOI: 10.5614/j.eng.technol.sci.2022.54.5.3 Issue No:Vol. 54, No. 5 (2022)
Authors:Atika Rahmahwati, Aryo Prawoto Wibowo, Fadhila Achmadi Rosyid Pages: 220504 - 220504 Abstract: Indonesia is a leading producer of a wide range of minerals, including copper. Nonetheless, the copper-based industry in Indonesia is still not well developed, especially the limited number of products from the intermediate copper industry which will become raw materials for its downstream industry. The underdeveloped intermediate copper industry has forced Indonesia to import several types of copper-based semi-finished products to meet the needs of the downstream industry. On the other hand, the mining industry still exports copper concentrate and some copper cathodes produced by smelting. As a result, the added value obtained by Indonesia from copper is not optimal. Therefore, it is necessary to conduct research on the copper industry chain and to estimate the increase in added value that could be generated. In this study, a system dynamics (SD) model was developed. During the simulation period of 2020 to 2030, the total added value along the copper industry chain that can be obtained is USD 70,422,840,000 if the planned smelter and refinery is completed in 2023 to process all domestic concentrates and to increase intermediate industry capacity. PubDate: 2022-09-05 DOI: 10.5614/j.eng.technol.sci.2022.54.5.4 Issue No:Vol. 54, No. 5 (2022)
Authors:Heri Rustamaji, Tirto Prakoso, Hary Devianto, Pramujo Widiatmoko Pages: 220505 - 220505 Abstract: The supercapacitor has gotten a lot of attention as a high-performance energy storage device because of its high power density, good energy density, long life cycle, and extensive application in various electronic applications. To effectively assess its performance, the electrode material composition was optimized with a blend of activated carbon (AC), multiwall carbon nanotube (MWCNT), and graphene (GR). The synergistic effect of AC, CNT, and GR supports the usage of AC/MWCNT/GR as a viable supercapacitor electrode. Furthermore, the surrounding MWCNT enhances AC and GR electronic conductivity, while AC efficiently suppresses GR re-stacking sheets and aggregates MWCNT particles. For supercapacitor electrodes, the optimal composite mixtures of AC, MWCNT, and GR were 71.7%, 20%, and 8.3% wt, respectively. Meanwhile, an outstanding capacitance value of 33.5 F g-1 in 6 M KOH electrolyte was obtained at 2 mV s-1. PubDate: 2022-09-05 DOI: 10.5614/j.eng.technol.sci.2022.54.5.5 Issue No:Vol. 54, No. 5 (2022)
Authors:Muhammad Arif Asadi, Feni Iranawati, Fairus Nafidya, Supriyadi Supriyadi, Avijit Talukder Pages: 220506 - 220506 Abstract: The contamination of microplastics have been reported in a wide array of marine organisms, including bivalve molluscs. This study aimed to investigate the occurrence and abundance of microplastics in bivalves from coastal waters of Paciran, Lamongan, East Java, Indonesia. High population and anthropogenic activities in the area may lead the contamination of microplastics in its marine organisms. Microplastics were recovered from the soft tissues of three species of wild clams, Gafrarium tumidum, Anadara antiquata, and Venerupis philippinarum. In each species, microplastics were grouped based on their types and sizes. The extraction of microplastics was using 30% H2O2, while flotation method using NaCl was used to separate the dissolved liquid of the clam’s soft tissues. Microplastic ingestion was found in 99.23% of the clam samples with average concentration of 3.5 ± 2.8 items/individual and 3.2 ± 2.52 items/g. V. philippinarum had the highest microplastics concentration (4.9 ± 2.80 items/g and 5.6 ± 3.22 items/individual). Microplastic types from all samples were dominated by fibers (80.77%), in which 57% of them were less than 200 µm in size. The ubiquitous contamination of microplastics in clams of the coastal waters of Lamongan, Indonesia is serious concerns for marine food webs and human health. PubDate: 2022-09-06 DOI: 10.5614/j.eng.technol.sci.2022.54.5.6 Issue No:Vol. 54, No. 5 (2022)
Authors:Muhammad Saafan, Mysara Mohyaldinn , Khaled Elraies Pages: 220507 - 220507 Abstract: Capillary pressure is a crucial input in reservoir simulation models. Generally, capillary pressure measurements are expensive and time-consuming; therefore, there is a limitation on the number of cores tested in the laboratory. Accordingly, numerous capillary pressure models have been suggested to match capillary pressure curves and overcome this limitation. This study developed a new fractal capillary pressure model by depicting the porous system as a bundle of tortuous triangular tubes. The model imitates the pores’ angularity, providing a more accurate representation of the pore system than smooth circular openings. Moreover, triangular tubes allow the wetting phase to be retained in the tube’s corners. A genetic algorithm was employed to match the capillary pressure curves and obtain the proposed model’s parameters. Capillary pressure data of eight low-permeability sandstone samples from the Khatatba formation in the Western Desert of Egypt were utilized to test the proposed model. The results revealed that the developed model reasonably matched the laboratory-measured data. PubDate: 2022-09-09 DOI: 10.5614/j.eng.technol.sci.2022.54.5.7 Issue No:Vol. 54, No. 5 (2022)
Authors:Muhammad Ihsan Abyan, Aang Nuryaman, Bagus Hayatul Jihad, Soleh Fajar Junjunan, Asmiati Asmiati Pages: 220508 - 220508 Abstract: A rocket is a spacecraft, guided missile, or flying vehicle that boosted by a chemical reaction resulting from the combustion of propellant in the rocket motor. One of the essential parameters in the development of rocket motors is design optimization to improve the propulsion performance of the rocket. Increasing the propulsion performance of the rocket will increase the flight performance of the rocket, in terms of its maximum range or the altitude of the rocket trajectory. This study examined the determination of the design parameter values of a rocket motor by looking at it as an optimization problem with constraints. The problem studied was limited to the case of the second-stage rocket motor. A genetic algorithm was used to solve the resulting optimization problem of propellant grain configuration cases and a characteristic method for designing the bell nozzle. The results obtained indicated an increase in total impulse by 10% compared to the results before optimization. PubDate: 2022-09-15 DOI: 10.5614/j.eng.technol.sci.2022.54.5.8 Issue No:Vol. 54, No. 5 (2022)
Authors:Buragadda Kiran Kumar, Vemulapalli Chittaranjan Das Pages: 220509 - 220509 Abstract: Wire Electric Discharge Machining (WEDM) is a non-traditional machining method that is widely used in the manufacture of aerospace/aircraft and medical equipment for conductive materials. WEDM products are expected to have good dimensional accuracy, surface roughness, and geometry. Many researchers have done experiments on various materials to optimize the process, which has many parameters and response characteristics. This paper provides an overview of the WEDM process on alloy steels in order to understand the impact of input process variables on output responses and optimization techniques for selecting optimal process parameters. This paper also highlights WEDM process trends as well as workpiece materials, wire varieties, wire diameters, and optimization approaches. This work is expected to be useful in initiating further research on WEDM by documenting substantial research works confirming the latest scenario. PubDate: 2022-09-15 DOI: 10.5614/j.eng.technol.sci.2022.54.5.9 Issue No:Vol. 54, No. 5 (2022)
Authors:Muhaned Zaidi Pages: 220510 - 220510 Abstract: Two bulk-driven CMOS (Complementary Metal Oxide Semiconductor) operational amplifier (op-amp) designs for electrocardiogram (ECG) application are presented and compared in this paper. Both op-amps are based on two-stage amplification, where bulk-driven differential input is the first stage, while additional DC gain is the second stage. Different compensation techniques were integrated in each op-amp design. Standard Miller compensation was used for the first op-amp parallel with the second stage. The novelty of the second op-amp is that it utilizes negative Miller compensation between the bulk-driven input node and the output node of the first stag, while standard Miller compensation was used in the second stage. The purpose of this work was to compare DC gain, phase margin (PM) and unit gain frequency (UGF) obtained through different simulated compensation strategies and test results. The op-amps were simulated using 0.25 μm CMOS technology. The simulation results are presented using the standard model libraries from Tanner EDA tools, operating on a single rail +0.8V power supply. PubDate: 2022-09-15 DOI: 10.5614/j.eng.technol.sci.2022.54.5.10 Issue No:Vol. 54, No. 5 (2022)
Authors:Nguyen Phu Thuong Luu, Ly Hung Anh Pages: 220511 - 220511 Abstract: This study simulated and evaluated the safety of a small car structure in a collision with the rear of a truck. The parameters of bumpers currently used in Vietnam were employed to build a model of the rear truck bumper. The setting of simulation conditions was based on the NCAP (New Car Assessment Program) crash test. According to actual crash conditions, a collision simulation was performed with different vehicle speeds from 40 to 60 km/h, corresponding to the case of a passenger vehicle moving in a city colliding with a truck standing still. In addition, the percentage of rear-end collision was also taken into account, just like in real-world collisions, at 25%, 50%, and full rear impact. The simulation results were analyzed and evaluated according to the IIHS rating (Institute Insurance for Highway Safety). The results from different case studies showed that the rear bumper typically used on trucks is only safe for passenger cars in a collision at a low speed of 40 km/h and that in a collision at a higher speed will affect the passenger’s safe space and cause high injuries and casualties. Therefore, it is necessary to improve safety by optimizing the rear bumper design and the frontal structure of the small car chassis. PubDate: 2022-09-15 DOI: 10.5614/j.eng.technol.sci.2022.54.5.11 Issue No:Vol. 54, No. 5 (2022)
Authors:Mutiara Fajar, Emenda Sembiring, Marisa Handajani Pages: 220512 - 220512 Abstract: Microplastics (MP) can pose a serious threat to the environment and human health because of their tiny size and ability to spread easily in water. One of the alternative treatments to remove MP from water is the rapid sand filter (RSF). The objective of this study was to analyze the effects of filter media size and loading rate on RSF performance in removing MP. The applied filter media was silica sand with effective sizes (ES) of 0.39 and 0.68 mm. The loading rates of filtration were 4; 6; 8 and 10 m3/m2-h. The MP samples were made from plastic bags and torn tires (artificial samples: 10 to 800 µm). This study showed that the MP removal percentage was up to 96.6% (MP size larger than 200 µm). The head loss increment for loading rates 4; 6; 8; 10 m3/m2-h was 0.16; 0.35; 0.34; 0.25 m (ES 0.39 m) and 0.10; 0.18; 0.18; 0.19 m (ES 0.68 m)), respectively. Meanwhile, the filtration cycle for loading rates 4; 6; 8; and 10 m3/m2-h was 5, 2, 2, and 1 days (ES 0.39 mm) and 9, 4, 3, and 3 days (ES 0.68 mm), respectively. The result of this study showed that the smaller the filter media size, the higher the head loss of the filter media bed. Furthermore, there is an increased head loss of the filter media bed when the loading rate is greater. PubDate: 2022-09-15 DOI: 10.5614/j.eng.technol.sci.2022.54.5.12 Issue No:Vol. 54, No. 5 (2022)
Authors:Anggit Raksajati, Haditya Kukuh Purwanto, Ardian Nugra Baskoro, Antonius Indarto, Danu Ariono Pages: 220513 - 220513 Abstract: Acid gas enrichment unit (AGEU) involves selective separation of H2S from acid gas mixture, for example using absorption with an NaOH solvent solution. Sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) buffer addition to NaOH solution suppresses CO2 absorption, thereby increasing the selectivity of H2S absorption. This study evaluated the effect of buffer addition to increase H2S absorption selectivity using an NaOH solution. It was shown that both buffer addition and L/G ratio decrease could increase H2S selectivity by limiting CO2 absorption. Based on the simulation results, in the 0.006 to 0.030 L/G ratio range and NaOH solvent concentration greater than 2%-mass, the addition of NaHCO3 with mass ratio greater than 1.5:1 to NaOH and the addition of Na2CO3 at 1.26 times NaHCO3’s mass increased H2S absorption selectivity up to 17.3%. The combination of an L/G ratio of 0.006 and solvent with a composition of 5%-mass NaOH, 15%-mass NaHCO3, and 18.9%-mass Na2CO3 produced the highest H2S selectivity of 23.1 (379.7% H2S selectivity increase). PubDate: 2022-09-16 DOI: 10.5614/j.eng.technol.sci.2022.54.5.13 Issue No:Vol. 54, No. 5 (2022)
Authors:Lusi Ernawati, Ruri Agung Wahyuono, Abdul Halim, Nurul Widiastuti, Audi Sabrina, Kurnia Handayani Pages: 220514 - 220514 Abstract: Groundwater highly contaminated with organic substances and heavy metal ions in the Kariangau Industrial Area, Balikpapan, East Kalimantan is indicated by the comparatively high COD. Therefore, the technology for treating wastewater to remove various toxins before releasing it into the environment needs to be advanced. Here, we present a green synthetic method of a composite adsorbent (SF/SS) using soursop seeds and silkworm cocoons. SEM, FTIR, and BET were used to analyze the physicochemical characteristics of the adsorbent. Mechanistic investigation of the SF/SS adsorbent performance for the removal of Cu2+ metal ions and crystal violet (CV) was conducted, while taking into account variables affecting adsorption properties. The Freundlich and Langmuir isotherm adsorption models were used to fit the adsorption equilibrium, while pseudo-first and second-order models were used to assess the adsorption kinetics. The mesoporous SF/SS adsorbent exhibited the highest adsorption capacities of 78.6 and 69.2 mg‧g-1, respectively. The pseudo-first model showed the best fit for CV removal with a kinetic rate of 0.0634 min-1, while the Freundlich model exhibited the best fitting for both of CV and Cu2+ removal. The results showed that SF/SS can be applied as an efficient adsorbent for both of heavy metal and organic dye removal. PubDate: 2022-09-16 DOI: 10.5614/j.eng.technol.sci.2022.54.5.14 Issue No:Vol. 54, No. 5 (2022)
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