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Makara Journal of Technology
Published by Universitas Indonesia
ISSN : 23552786     EISSN : 23564539     DOI : https://doi.org/10.7454/mjt
Core Subject : Science, Engineering,
Chemical Engineering, Chemistry & Bioengineering Civil Engineering, Building, Construction & Architecture Electrical & Electronics Engineering Engineering Materials Science & Nanotechnology Mechanical Engineering
MAKARA Journal of Technology is a peer-reviewed multidisciplinary journal committed to the advancement of scholarly knowledge and research findings of the several branches of Engineering and Technology. The Journal publishes new results, original articles, reviews, and research notes whose content and approach are of interest to a wide range of scholars. It also offers rapid dissemination. MAKARA Journal of Technology covers the recent research in several branches of engineering and technology include Electrical & Electronics Engineering, Computer Engineering, Mechanical Engineering, Chemical & Bioprocess Engineering, Material & Metallurgical Engineering, Industrial Engineering, Civil & Architecture Engineering, and Marine Engineering. Criteria used in determining acceptability of contributions include newsworthiness to a substantial part of the engineering & technology and the effect of rapid publication on the research of others. This journal, published three times each year, is where readers look for the advancement of discoveries in engineering and technology.
Arjuna Subject : Teknik (semua kategori) - Teknik (Lain-Lain)
Articles 5 Documents
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Search results for , issue "Vol. 28, No. 3" : 5 Documents clear
Effect of Different Pressures on Polymer Flow at a Contraction Path: A Real-Time Numerical Approach Azmi, Muhammad Afiq; Ariff, Zulkifli Mohamad; Shuib, Raa Khimi; Rusli, Arjulizan; Ku Ishak, Ku Marsilla; Shafiq, Mohamad Danial; Hamid, Zuratul Ain Abdul; Zakaria, Zulfirdaus; Abu Bakar, Muhamad Husaini; Abdullah, Muhammad Khalil
Makara Journal of Technology Vol. 28, No. 3
Publisher : UI Scholars Hub

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Abstract

The complexity of polymer flow through a contraction arises from the simultaneous occurrence of shear and elongational strains near the entrance of the contraction path (die). Although this phenomenon has been extensively studied, the effect of plunger motion on the flow toward the contraction path remains underexplored. This study investigated the rheological behavior of thermoplastic polymers at a contraction flow path to enhance the understanding of their flow and rheological behavior, including variations in velocity, pressure, viscosity, and shear rate under varying loads. Polypropylene (PP), a semicrystalline polymer with a low melting point, was used as the test material. The operating temperature was set to 180 °C, and the displacement of the plunger, marked with black lines at its initial and final heights, was recorded under loads of 0.3, 0.6 and 0.85 MPa. The displacement rates were analyzed using MATLAB. A dynamic mesh approach in ANSYS 19 was employed to simulate the real-time motion of the plunger, incorporating a user-defined function developed in C language to control the dynamic boundary motion. The numerical approach successfully simulated the rates of plunger displacement (speed) and predicted the viscosity of PP within the paths (barrel and die). Results indicated that the plunger speed increased with pressure. The pressure generated by the plunger created a driving force that overcame the resistance to flow within the barrel. Higher pressure from the plunger resulted in a greater driving force, which increased the flow rate of the polymer melt through the barrel. On the other side, as the polymer melt flowed from a large cross-sectional area to the contraction flow area, the velocity of the polymer molecules increased, resulting in a pressure drop in the PP melt. Polymer molecules became oriented and stretched in the flow direction upon entering the contraction area, further increasing the shear rate. Consequently, the reduced cross-sectional area in the contraction increased the flow rate, elevated the shear rate, and decreased the viscosity, facilitating polymer flow through the contraction.
Determination of the Kinetic Parameters of Cholesterol Oxidation using Cholesterol Oxidase from Streptomyces sp. Perdani, Meka Saima; Hermansyah, Heri; Sahlan, Muhamad; Putri, Dwini Normayulisa; Pambudi, Teguh; Hasibuan, Anggi Khairina Hanum
Makara Journal of Technology Vol. 28, No. 3
Publisher : UI Scholars Hub

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Abstract

Cholesterol oxidase (CO) was successfully produced from Streptomyces sp. via the submerged fermentation method, and 69 U/mL enzyme activity was obtained. This study aimed to determine cholesterol oxidation kinetics and the production of CO as a catalyst. The enzyme was diluted to 0.15, 0.075, and 0.00375 U/mL for the oxidation reaction. The substrate was also prepared in three concentrations: 3.23, 6.46, and 12.93 mM. The optimization of conditions for enzymatic cholesterol oxidation was investigated through measurement of the effect of initial cholesterol and enzyme concentrations. Cholesterol concentration was rapidly measured via high-performance liquid chromatography (HPLC). The kinetics of CO were modeled using the first-order irreversible reaction. An enzymatic kinetic model was derived, and it was verified using experimental data and sensitivity analysis. Based on the experiment, the highest enzyme concentrations of crude and commercial CO can oxidize the substrate up to 84% within 240 min. However, the oxidation reaction showed a slightly different behavior in the early 60 min, and crude CO exhibited a slower substrate oxidation. The kinetic rate constant obtained by Euler’s method reached 1.0 x 10−3/min and 1.41 x 10−3/min for 0.15 U/mL crude and commercial CO, respectively.
Liquid-Cooled Thermoelectric Modules: Potential for Efficient Water Harvesting Through Air Condensation Prasetyo, Bowo Yuli; Yuliane, Aindri; Rosulindo, Parisya Premiera; Wang, Fujen
Makara Journal of Technology Vol. 28, No. 3
Publisher : UI Scholars Hub

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Abstract

Water is one of the essential natural resources for the sustaining life of all beings on this planet. In general, groundwater is used to meet daily needs, although the availability of this water source becomes a major concern, particularly in some areas with limited access to it. Air condensation is a solution for providing water in such areas. This study aims to explore the potential of utilizing the thermoelectric technology as an alternative solution for water provision. An experiment is conducted using a system consisting of single liquid-cooled thermoelectric cooling devices/modules (TECs). Three types/variants of TECs with different cooling capacities are tested at three different operating voltages. During the tests, changes in physical quantities are recorded for analysis, along with amount of water produced. The results demonstrate notable performance differences between all TEC variants. The highest cooling capacity is achieved by the TEC-1 variant, albeit with higher current usage. The TEC-3 variant delivers the lowest performance of all. TEC-2 obtains the highest water yield, producing 46.9 g of water at 12 V, while TEC-1 and TEC-3 produce 34.4 and 13.2 g, respectively. The highest condensation rate, i.e., 3.72%, is achieved by TEC-2, at 9 V, while the lowest energy consumption, i.e., 3.74 kWh/L, is shown by TEC-2, at 12 V.
Design Modeling and CFD Simulation of Parallel Plate–Fin Heat Sink Under Natural Convection Nguyen, Tue Duy; Vo, An Van; Bui, Tam Thanh
Makara Journal of Technology Vol. 28, No. 3
Publisher : UI Scholars Hub

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Abstract

The lifetime of electronic devices strongly depends on the junction temperature. Heat sinks are a good choice for dissipating heat because of their enhanced heat transfer areas. Plate–fin heat sinks are commonly used for electronic components because of their simple construction. Recently, computational fluid dynamics (CFD) software, such as Ansys Fluent and OpenFOAM, has been widely used and has provided effective results. Autodesk CFD is a powerful simulation tool; however, its use in heat sink research remains relatively uncommon. In this study, two plate–fin heat sinks with heights of 30 and 50 mm were first designed using heat transfer equations and then compared with Autodesk CFD simulations under natural convection conditions. Temperature inputs of 60 °C, 70 °C, and 80 °C were assigned to determine the temperature distribution along the fins, heat dissipation, fin efficiency, and fin effectiveness for both types of heat sinks. The results of the heat transfer calculations and Autodesk CFD simulations are consistent, with negligible differences. These findings indicate that Autodesk CFD can produce reliable results for heat sink design. In addition, efficiency decreases with the increase in fin height, although the effectiveness and heat dissipation of the tall (50 mm) heat sink are higher than those of the short (30 mm) heat sink. Although the 50-mm-high fin heat sink has a heat transfer area approximately 63% larger than that of the 30-mm-high fin heat sink, its heat dissipation is only approximately 40% larger than that of the 30-mm-high fin heat sink. This finding indicates that the addition of more material alone may not proportionally increase heat transfer and could lead to wasted material. Therefore, when designing heat sinks, the height of the fins should be carefully considered and optimized to enhance efficiency and conserve materials.
Smart Materials for Noise and Vibration Damping in High-Speed Rail Systems: A Comparative Analysis Unegbu, Hyginus Chidiebere Onyekachi; Yawas, Danjuma Saleh; Dan-asabe, Bashar; Alabi, Abdulmumin Akoredeley
Makara Journal of Technology Vol. 28, No. 3
Publisher : UI Scholars Hub

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Abstract

Effective noise and vibration control remains a critical challenge in high-speed rail systems, directly influencing passenger comfort and the longevity of infrastructure. This study evaluated four advanced materials—piezoelectric materials, shape memory alloys (SMAs), magnetorheological (MR) fluids, and damping composites—focusing on their potential for mitigating noise and vibration in high-speed rail applications. A combination of experimental and simulation-based analyses was employed to assess these materials based on their noise reduction coefficient, vibration transmissibility ratio, thermal stability, and durability under varying environmental conditions. The findings revealed that damping composites and SMAs demonstrated superior performance, offering enhanced noise attenuation and vibration control compared with the other materials. Damping composites exhibited the highest noise reduction and stability across a wide frequency range, while SMAs demonstrated exceptional adaptive damping properties under fluctuating temperature conditions. In contrast, piezoelectric materials and MR fluids showed moderate performance, making them more suitable for secondary damping applications. This study identifies damping composites and SMAs as the most effective materials for primary noise and vibration control in high-speed rail systems. The findings provide valuable insights for material selection and integration in rail infrastructure, contributing to enhanced system performance, reduced maintenance costs, and compliance with stringent noise and vibration regulations.

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