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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. 27, No. 3" : 5 Documents clear
Heat Transfer Enhancement in Nanofluid Flows Augmented by Magnetic Flux Arjun, Kozhikkatil Sunil; Kumar, Rakesh
Makara Journal of Technology Vol. 27, No. 3
Publisher : UI Scholars Hub

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Abstract

Heat transfer enhancement could be realized using magnetohydrodynamics together with nanofluids specifically in flow micro-convection in a microtube, flow past a vertical porous plate, and square duct flow with discrete heat sources numerically. A critical value for the Rayleigh number, a maximum value for the magnetic field strength, a low Reynolds number, and volume concentrations exists for thermal enhancement to simulate nanofluid flow in a microtube. Heat transfer enhancement is observed with a reduction in the magnetic field strength in a flow past a heated porous vertical plate. Alumina nanofluid subjected to Hartmann number 10 can boost 81% enhancement in Nusselt number in a square duct at lower Reynolds number using three discrete heat sources under the impact of thermal and solutal buoyancy. A 4% increase in the cooling effect near the center of the last heat source in a nanofluid flow is of practical use in hot spot cooling.
Effect of Lime Content, Curing Temperature, and Aging Condition on Low-Alkaline Concrete Pour, Mahdi Parsa; Sharghi, Reza Shaban; Nejati, Faezeh; Najafi, Elmira Khaksar
Makara Journal of Technology Vol. 27, No. 3
Publisher : UI Scholars Hub

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Abstract

This study determines how curing temperatures, aging condition, and hydrated lime contents affect the unconfined compressive strength (UCS), modulus of elasticity, and workability of low-alkaline concrete. Samples were prepared in two different groups to determine the optimum hydrated lime content and aging conditions to assess the mutual effect of NaOH molarity and curing temperature, that is, 70 °C for 48 h or room temperature, on samples with and without lime. The results showed that the increase in hydrated lime content affected alkali concentration. The samples with lime exhibited a clear peak in UCS (6 M NaOH) compared with the continuous increase for the samples without lime. Lime content had a positive effect on eliminating heat curing and prolonging aging time to enhance the Young’s modulus and compressive strength. This result is promising for in-situ concreting. Similar to the effect of alkali concentration, lime contributed to the loss in slump value. The scanning electron microscopy images showed the formation of N-(C)-A-S-H gels as the main reaction products. Moreover, internal cracking contributed to the lower UCS of samples with 9 M NaOH compared with those with 6 M NaOH.
Isolation and Characterization of Caffeine-Degrading Bacteria from Coffee Plantation Areas in Malaysia Dullah, Elvina Clarie; Farida Asras, Mohd Fazli
Makara Journal of Technology Vol. 27, No. 3
Publisher : UI Scholars Hub

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Abstract

Decaffeination by microbial degradation is currently the most optimal and low-cost approach, involving only microbial cells and/or their enzymes. The bacterium was characterized using a series of biochemical tests. Positive results were obtained from carbohydrate fermentation, citrate utilization, and catalase tests, while negative results were obtained from Voges-Proskauer (VP) and indole tests. Three different caffeine concentrations of 0.25%, 0.4%, and 2% were tested and measured through Gas Chromatography-Mass Spectrophotometry (GC-MS) analysis. The highest caffeine reduction (89.25%) was found when 0.25% caffeine was used in the media. Only a small amount of caffeine was reduced to 0.4% and 2%, with 34.78% and 46.16%, respectively. Under microscopic observation, the shape of the isolated bacteria was rod bacilli and was stained with a pink color, which indicates Gram-negative bacteria. Comparing the results with previous research and observing the color of the pure culture, which revealed a yellow color, bacteria isolated from the coffee plantation area can be concluded to be a partially identified Pseudomonas sp.
Briquette of Empty Fruit Bunch Fiber as an Alternative Substitution for Binderless Fuel Methods Handra, Nofriady; Indra, Ade
Makara Journal of Technology Vol. 27, No. 3
Publisher : UI Scholars Hub

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Abstract

Biomass development has been a key issue for the past few decades and will remain attractive in the future because of its cleanliness, renewability, carbon neutrality, and other advantages. This study aims to determine the optimal holding time for heating system briquettes by testing the heating value of empty fruit bunches fibers. The process of this research involves the use of one unit of briquette molding equipment by providing a heating system to the mold cylinder. Fibers were manually finetuned until they reached a size of 20 mesh (0.84 mm). Densification temperature is an essential factor that could affect the combustion properties, especially the calorific value. The Arduino program is used for setting the heating resistance time of the mold, which is 15, 20, and 25 min at a temperature of 200 ºC, and the thermal controller is used to adjust the temperature variation. Results showed that the highest calorific value of the three varieties of holding time was at 25 min with a calorific value of 4480.2 cal/g, and the lowest cost at 15 min was 4022 cal/g. Meanwhile, a calorific value of 4432.5 cal/g was found at 20 min. This finding is due to the low moisture content and high charcoal content of the sample in the 25 min briquette mold. Therefore, briquettes at 25 min have a higher heating value compared with those at 15 and 20 min holding time.
Optimization of the Building Envelope and Roof Shading to Reduce the Energy Consumption of College Low-Rise Buildings in Indonesia Nasruddin, Nasruddin; Alam, Azimil Gani; Sohel, Mohammad Imroz
Makara Journal of Technology Vol. 27, No. 3
Publisher : UI Scholars Hub

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Abstract

Energy consumption in buildings is a crucial concern globally, prompting researchers to explore innovative solutions to mitigate its impact. This study investigates the optimization of building envelopes and roof shading systems of existing buildings in Indonesia to realize notable energy savings. Multiple scenarios were explored, with modifications to building envelopes and roof shading, highlighting the overall thermal transfer value as a key parameter. Using EnergyPlus simulations, the efficacy of natural ventilation in corridors and roof shading modifications was assessed in reducing energy consumption. The findings revealed that renovating existing buildings by optimization of the building envelope and roof shading by simulations can contribute considerably to energy conservation. Various scenarios produced distinct energy savings, underscoring the importance of empirically planned modifications. Substantial reductions in energy and even water consumption were realized by applying natural ventilation in corridors and modifying roof shading, demonstrating a promising approach. Furthermore, avenues for future research were discussed, pointing toward the need for comprehensive analyses of diverse building types, climates, and geographical locations. This study can serve as foundational step toward developing practical guidelines for energy-saving retrofits in existing buildings in Indonesia and similar climate.

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