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INDONESIA
Makara Journal of Technology
Published by Universitas Indonesia
ISSN : -     EISSN : -     DOI : -
Core Subject : Science,
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Articles 8 Documents
Search results for , issue " Vol 19, No 3 (2015)" : 8 Documents clear
Dual-Band Singly-Fed Proximity-Coupled Tip-Truncated Triangular Patch Array for Land Vehicle Mobile System Basari, Basari; Sumantyo, Josaphat Tetuko Sri
Makara Journal of Technology Vol 19, No 3 (2015)
Publisher : Directorate of Research and Community Services, Universitas Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (166.696 KB) | DOI: 10.7454/mst.v19i3.3223

Abstract

This paper proposes a dual-band left-handed circularly polarized triangular-patch array that is developed for land vehicle mobile system aimed at mobile satellite communications. The array consists of six tip-truncated triangular patches, which the first three patches are used for reception and the second three patches are used for transmission purpose. Each of three-patches has a beam pattern that can be switched in three different 120°-coverage beam in azimuth-cut plane at a minimum targeted gain at a desired elevation angle. The targeted minimum gain of the array is 5 dBic, in order for data communications with a large geostationary satellite can be achieved. The array is able to operate in two different frequency bands i.e. 2.50 GHz band for reception (down-link) and 2.65 GHz band for transmission (uplink). The array is simulated using the Method of Moments-based software (Ansoft Maxwell), fabricated and measured to confirm the simulated results. The measurement results show that the 5dBic-gain and the 3dB-axial ratio of the reception elements cover all of 360° azimuth direction. In the case of transmission elements, 4.3dBic-gain and the 3dBaxial ratio can be obtained. 
Calibration of Numerical Model for Shoreline Change Prediction Using Satellite Imagery Data Sutikno, Sigit; Murakami, Keisuke; Handoyo, Dwi Puspo; Fauzi, Manyuk
Makara Journal of Technology Vol 19, No 3 (2015)
Publisher : Directorate of Research and Community Services, Universitas Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (609.854 KB) | DOI: 10.7454/mst.v19i3.3219

Abstract

This paper presents a method for calibration of numerical model for shoreline change prediction using satellite imagery data in muddy beach. Tanjung Motong beach, a muddy beach that is suffered high abrasion in Rangsang Island, Riau province, Indonesia was picked as study area. The primary numerical modeling tool used in this research was GENESIS (GENEralized Model for Simulating Shoreline change), which has been successfully applied in many case studies of shoreline change phenomena on a sandy beach.The model was calibrated using two extracted coastlines satellite imagery data, such as Landsat-5 TM and Landsat-8 OLI/TIRS. The extracted coastline data were analyzed by using DSAS (Digital Shoreline Analysis System) tool to get the rate of shoreline change from 1990 to 2014. The main purpose of the calibration process was to find out the appropriate value for K 1 and K coefficients so that the predicted shoreline change had an acceptable correlation with the output of the satellite data processing. The result of this research showed that the shoreline change prediction had a good correlation with the historical evidence data in Tanjung Motong coast. It means that the GENESIS tool is not only applicable for shoreline prediction in sandy beach but also in muddy beach.
Improvement of Quality of Carica papaya L. with Clove Oil as Preservative in Edible Coating Technology Kusrini, Eny; Usman, Anwar; Wisakanti, Chrispine Deksita; Arbianti, Rita; Nasution, Dedy Alharis
Makara Journal of Technology Vol 19, No 3 (2015)
Publisher : Directorate of Research and Community Services, Universitas Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (134.64 KB) | DOI: 10.7454/mst.v19i3.3224

Abstract

We have studied utilization of essential clove oil, extracted from clove buds by hydrodistillation, as preservative in edible packaging technology. Preservative of essential clove oil was applied on chopped papaya fruits by using two methods, namely spray and brush. The effects of concentration of clove oil from 0.05 to 0.20% on the preservation of papaya fruits (Carica papaya L.) at room temperature (25 °C) were also evaluated. Physicochemical and in vitro microbiological activities on the papaya fruits that were stored at 25 oC and 85-90% relative humidity were investigated in details. The results indicate that the clove oil at concentration ≥0.10% suppressed the decay time, 10% weight loss, 0.03 g citric acid/100 g in acidity titration test, and 20% pH value from those of control sample of papaya fruits kept in a storage. The population of fungi and bacteria were efficiently reduced by 90% when the clove oil at concentration ≥0.10% was applied as preservative on papaya fruits. This finding suggested that the extracted essential clove oil acted as effective antifungal and antibacterial agents. Preservative by essential clove oil improved the quality of fruits to extend the product shelf life and to reduce the risk of microbial growth on fruits surface.
Oxidation Process of H 2 O /UV for COD Reduction of Wastewater from Soybean Tofu Production Pontas, Komala; Muslim, Abrar
Makara Journal of Technology Vol 19, No 3 (2015)
Publisher : Directorate of Research and Community Services, Universitas Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (510.049 KB) | DOI: 10.7454/mst.v19i3.3220

Abstract

Chemical Oxygen Demand (COD) reduction of wastewater from soybean tofu production was studied by conducting advanced oxidation process (AOP) using hydrogen peroxide with UV radiation catalysts in a closed cylindrical glass reactor. The hydroxyl radical (*OH) concentration from H2O decomposition was modeled, and exponential trends were found for the *OH concentration over radiation time and operation temperature. As a result, it was found that the maximal *OH concentration was 0.209 mol L-12 at 240 minutes and 50 °C. The *OH concentration exponentially increased following rise in operation temperature. The H2O /UV AOP application reduced COD concentration to approximately 42.41% from 10,545 to 6,073.2 mol L-12 at 240 minutes and 50 °C. In addition, the pseudo second order kinetics is a reliable model to present the COD reduction kinetics with the correlation coefficient R in the range of 95.9 to 99.4%. The kinetics constant increased with rise in operation temperature, and it was approximately 2.30E-07, 2.590E-07, and 3.03E-07 L mg-1 min-1 for 30, 40, and 50 °C, respectively. The activation energy of COD reduction obtained was approximately 0.0138 J mol-1.
Uplift of Shoreline Regions on Pagai Island due to the September 12, 2007 Mw 8.4 Earthquake Captured by SAR Image Lubis, Ashar Muda
Makara Journal of Technology Vol 19, No 3 (2015)
Publisher : Directorate of Research and Community Services, Universitas Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1680.407 KB) | DOI: 10.7454/mst.v19i3.3221

Abstract

At least 25 people were killed by the September 12, 2007 Mw 8.4 Bengkulu earthquake, and many buildings were destroyed in Bengkulu and West Sumatra provinces. It is very important to estimate the earth surface deformation due to the earthquake to understand the rupture size and its process. The aim of this research is to estimate the shoreline change and vertical displacement on Pagai Island associated with the September 12, 2007 Mw 8.4 Bengkulu earthquake. The intensity of ALOS-PALSAR satellite images is used to access the pattern of displacement. The result shows that Pagai Island demonstrated huge uplift due to the earthquake. In general, the result of uplift in the shoreline regions derived from Synthetic Aperture Radar (SAR) image has a good agreement with other methods, such as in situ measurements, InSAR, and Global Positioning System (GPS) observations. This result implies that the earthquake fault location was very close to/around Pagai Island. Using this method, we can easily estimate the pattern of deformation in very remote and very wide areas without any equipment on the ground. The only limitation is the method cannot provide quantitative displacement.
Independency of Elasticity on Residual Stress of Room Temperature Rolled Stainless Steel 304 Plates for Structure Materials Parikin, Parikin; Allen, David
Makara Journal of Technology Vol 19, No 3 (2015)
Publisher : Directorate of Research and Community Services, Universitas Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (275.366 KB) | DOI: 10.7454/mst.v19i3.3217

Abstract

Mechanical strengths of materials are widely expected in general constructions of any building. These properties depend on its formation (cold/hot forming) during fabrication. This research was carried out on cold-rolled stainless steel (SS) 304 plates, which were deformed to 0, 34, 84, and 152% reduction in thickness. The tests were conducted using Vickers method. Ultra micro indentation system (UMIS) 2000 was used to determine the mechanical properties of the material, i.e.: hardness, modulus elasticity, and residual stresses. The microstructures showed lengthening outcropping due to stress corrosion cracking for all specimens. It was found that the tensile residual stress in a specimen was maximum, reaching 442 MPa, for a sample reducing 34% in thickness and minimum; and about 10 MPa for a 196% sample. The quantities showed that the biggest residual stress caused lowering of the proportional limit of material in stress-strain curves. The proportional modulus elasticity varied between 187 GPa and of about 215 GPa and was free from residual stresses.
Effect of Fly Ash Fortification in the Manufacture Process of Making Concrete towards Characteristics of Concrete in Sulfuric Acid Solution Saputra, Asep Handaya; Shohibi, Muhammad; Kubouchi, Masatoshi
Makara Journal of Technology Vol 19, No 3 (2015)
Publisher : Directorate of Research and Community Services, Universitas Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (250.635 KB) | DOI: 10.7454/mst.v19i3.3222

Abstract

Fly ash is a silica or alumino silica material that can be used as a constituent of cement in the concrete manufacturing process. Utilization of fly ash aims to improve durability and minimize the reduction of concrete’s compressive strength exposed to an acidic environment, which can be achieved through the pozzolanic reaction of fly ash with Ca(OH) within concrete. The reduced content of Ca(OH) through pozzolanic reaction will minimize the tendency of ettringite formation (compounds that cause deterioration and decrease the compressive strength of concrete). In order to determine the relation between fly ash replenishment into concrete with concrete’s characteristics (compressive strength and durability) under acidic environment, the research is conducted by varying the fly ash composition ranging from 0%, 5%, 25%, 50%, up to 75%, and the concentration of H22SO solution as an immersion medium ranging from 0%, 5%, 10%, up to 15% (v/v). The research is carried out by immersing the concrete samples for 4 days in H4 solution with various concentrations. Characterization of concrete’s durability and compressive strength is reviewed from the concrete’s weight loss percentage and reduction of concrete’s compressive strength percentage after immersion. Based on the research results, for each variation of H2SO concentration used, the minimum concrete’s weight loss percentage (maximum durability) and the minimum reduction of concrete’s compressive strength percentage is found in the use of fly ash by 75%. For each concentration variations of H42SO solution as an immersion medium ranging from 5%, 10%, up to 15% (v/v), the minimum concrete’s weight loss percentage was 0.47%, 0.87%, 1.28% (respectively), whilst the minimum reduction of concrete’s compressive strength percentage was 5.71%, 14.29%, 17.14% (respectively). It was concluded that the use of fly ash can improve the durability and minimize the reduction of compressive strength of concrete exposed to an acidic environment.
Improving Renewable Energy Transition Acceptance: A Simulation Gaming Approach on a Multi Actor Setting in the Netherlands Sutrisno, Aziiz; Vennix, Jac A. M.; Syaifudin, Noor
Makara Journal of Technology Vol 19, No 3 (2015)
Publisher : Directorate of Research and Community Services, Universitas Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (243 KB) | DOI: 10.7454/mst.v19i3.3218

Abstract

The Netherlands have tried very hard to increase their renewable energy sources (RES) shares to fulfill the European Union target in 2050. However, RES performance did not show the expected result as the performance declined in 2009 producing even wider gap compare to the target. The Dutch government’s tried to incorporate all interested stakeholders by forming the Dutch energy transition task force. Nevertheless, the task force’s result is also not showing a desirable trend. Key reasons behind the Dutch low RES performance are the lack of shared understanding and positive attitude toward RES development among interested actors. This research uses a role-playing game to increase shared understanding and positive attitude within the actors. The game set players in a competing role as the government, an energy company and the end user. Players were given the ability to make decisions on their respective area. A pilot study was then conducted to measure the effectiveness of the game. The pilot study showed the game increased actor’s individual understanding and shared understanding. Moreover, it also showed that the game increases actor’s positive attitude toward RES development in the Netherlands.

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