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Rekayasa: Jurnal Penerapan Teknologi dan Pembelajaran
Published by Universitas Negeri Semarang
ISSN : -     EISSN : 25276964     DOI : https://doi.org/10.15294/rekayasa
Core Subject : Education,
Other
REKAYASA journal publishes exciting articles from all fields of research and Engineering Science. The journals primary focus is on research practice and engineering processes utilizing biomass or factory waste. The engineering journal is an open-access peer-reviewed journal that publishes articles from all areas of Engineering and Science research.
Arjuna Subject : Umum - Umum
Articles 28 Documents
 1   2   3 
Evaluation of Seismic Vulnerability Index and Soil Classification in Sleman Regency Based on Microtremor Analysis and the HVSR Method Fadlika Widyantari, Elsa; Aryono Adhi, Mochamad; Rahma, Ilqia; Budi Wibowo, Nugroho; Mustami' Limayukha, Desi; El Farsiyyi, Bilqis; Sofyana Ulya, Rahmania
Rekayasa Vol. 21 No. 1 (2023)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v21i1.9959

Abstract

Kalasan District and Ngemplak District, located in Sleman Regency, Yogyakarta, are areas with significant seismic risk due to the subduction of the Indo-Australian and Eurasian plates south of Java Island. To support disaster mitigation and land-use planning, it is essential to understand the local geological structure and soil dynamic response. This study aims to evaluate the seismic vulnerability and soil classification using the Horizontal to Vertical Spectral Ratio (HVSR) method and Rayleigh wave ellipticity inversion modeling. Microtremor measurements were conducted at 27 points distributed across both districts. The HVSR method was used to obtain the dominant frequency and amplification values, while the ellipticity inversion of Rayleigh waves was employed to estimate the shear-wave velocity profile and calculate Vs₃₀ values. The results show that the dominant frequency ranges from 0.713 Hz to 18.006 Hz, amplification values range from 0.569 to 4.193, and the seismic vulnerability index ranges from 0.010 to 12.060. Based on these parameters, Sleman Regency is generally categorized as having low to moderate seismic damage potential due to the relatively low amplification and vulnerability index. The Vs₃₀ values indicate a variation in soil site classes, namely medium-density soil (SD) and very dense soil (SC). These findings provide essential data for seismic microzonation, contributing to more resilient urban development strategies. 
Evaluation of Structural Features and Hydrocarbon Reservoir Potential of the Baturaja Formation Using Seismic Envelope and Sweetness Attributes Alifa Tri Handayani; Aryono Adhi, Mochamad; Eka Nurcahya, Budi
Rekayasa Vol. 21 No. 2 (2023)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v21i2.19729

Abstract

The Afara Field is located around the South Sumatra Basin, which is estimated to contain oil and gas hydrocarbon deposits. The method that can be used for hydrocarbon reserve exploration is the seismic method. Interpretation analysis is carried out by analyzing seismic attributes to determine the amplitude value, shape, and position of seismic waves to identify depositional environments, fluvial or channels, carbonate buildups, to detect fractures and faults, and to provide a direct hydrocarbon indicator (DHI). In this study, the seismic attributes used are the envelope and sweetness attributes to identify the presence of reservoirs, and the ant-tracking attribute is used to identify fault structures around the study area. The results obtained from the analysis carried out on the envelope attribute are the presence of hydrocarbon deposit areas seen from the bright-spot which indicates that the resulting amplitude value is high. The amplitude value has a range of values ​​around 280,000 ms to 440,000 ms located around the UPI-40 and UPI-60 wells. This is validated by the sweetness attribute, which is characterized by the presence of a sweet spot with a value ranging from 60,000 ms to 80,000 ms. The results of the geometric attribute analysis revealed the presence of faults in the study area.
Identification of Hydrocarbon Reservoir Distribution Using Seismic Attributes: RMS Amplitude and Sweetness in the Bani Field, South Sumatra Basin Tamba, Shallsa Bella. W; Adhi, M. Aryono; Nurcahya, Budi Eka
Rekayasa Vol. 21 No. 2 (2023)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v21i2.20846

Abstract

The Bani Field is in the South Sumatra basin, which is considered to have potential hydrocarbon reserves. The seismic reflection method is one method that can be used to describe geological conditions. In addition, this method is also able to provide analyses related to the presence of hydrocarbon reserves in the form of oil and gas, where one of the analyses that can be used is seismic attributes. In this study, the seismic attributes used are the RMS Amplitude and the Sweetness attribute, both of which play a role in identifying subsurface structures and determining hydrocarbon indicators. This study was conducted to analyze the results of the application of the RMS amplitude attribute and the sweetness attribute in determining the distribution of hydrocarbon reservoirs and analyzing the results of the application of the variance attribute in detecting the fault structure of the Bani Field. From the results of the analysis using the RMS amplitude attribute, the Batu Raja Formation layer describes a good response with a yellow to reddish brown color scale with a value scale between 220,000 to 320,000 ms, while the Talang Akar Formation layer describes a good response with a value scale of 160,000 to 240,000 ms. The analysis using the sweetness attribute confirmed the interpretation of the RMS amplitude attribute, indicating the presence of hydrocarbons, as depicted by the sweet spot region. Meanwhile, the geometrical attribute analysis used, namely structural smoothing and variance attributes, helped map structures and identify faults.
Analyzing the Total Resistance and Wave Pattern of Purse Seine Vessels with Photovoltaic-Powered Naryanto, Rizqi Fitri; Bahatmaka, Aldias; Wibowo, Muhammad Yusuf; Ghyferi, Andi Abdullah; Fahmi, Fiqri Fadillah; Hyoung Cho, Joung
Rekayasa Vol. 22 No. 2 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i2.10634

Abstract

With 64.97% of its territory consisting of sea, Indonesia is one of the world's largest maritime nations and produces approximately 8.02 million tons of fish annually. Traditional fishing vessels play a crucial role in supporting livelihoods, yet their design is often based on hereditary methods rather than hydrodynamic optimization. This study uses catamaran hull forms as a design reference to analyze the total resistance and wave patterns of purse seine vessels with photovoltaic-powered systems. Computational methods are employed to predict vessel performance efficiently. The resistance analysis applies the Slender Body approach and Savitsky's mathematical model, supported by comparative studies for validation. Particular attention is given to the influence of chine configurations on resistance characteristics and wave formation. Results indicate that the addition of chines increases the Froude number and contributes to reducing total resistance. Among the variations, single chine geometry demonstrates the lowest resistance, making it the most efficient configuration for catamaran fishing vessels. While chine modifications affect the wave pattern, the hull maintains a relatively clean wake distribution. These findings highlight the potential for improving vessel design through careful chine geometry optimization combined with computational modeling. The study underscores the importance of modern hydrodynamic analysis in advancing traditional fishing vessels toward higher efficiency and sustainability. Future research is recommended to incorporate more advanced computational approaches, such as Computational Fluid Dynamics (CFD), examine water-hull interactions and enhance vessel performance under operational conditions.
Optimization of Water-in-Biodiesel  Emulsification of Palm Oil by Ultrasonic Method using  Respons Surface Methodology Fauzi, Dinda Adelia; Kusumaningtyas, Ratna Dewi; Widyastuti, Catur Rini; Veny, Harumi
Rekayasa Vol. 23 No. 1 (2025)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v23i1.31831

Abstract

Palm oil biodiesel offers a renewable alternative but has high viscosity and density. Emulsifying biodiesel with water reduces these drawbacks and lowers nitrogen oxide (NOx) emissions. This study aims to optimize the emulsification process of water-in-biodiesel emulsion made from palm biodiesel (B100) using an indirect ultrasonic method and the response surface methodology approach with a Box-Behnken design. Three main independent variables were examined: hydrophilic-lipophilic balance values (6, 7.5, and 9), water concentrations (9%, 12%, and 15% v/v), and surfactant concentrations (5%, 7%, and 9% v/v) with a combination of Tween 80 and Span 80 as surfactants. The experimental process involves the synthesis of biodiesel from palm oil through transesterification with the help of 100W ultrasonic power for 15 minutes at room temperature. The analysis was carried out on three main parameters: density, viscosity, and water droplet size on water-in-biodiesel. The results of laboratory tests and statistical modeling show the three independent variables have a significant effect on the physical properties of water-in-biodiesel. The optimization resulted in the best conditions at a hydrophilic-lipophilic balance value of 6.11, water concentration of 9.06%, and surfactant concentration of 5%, with density characteristics of 859.95 kg/m³, kinematic viscosity of 4.44 mm²/s, and average water particle size of 4.46 μm, values close to conventional diesel fuel standards. This study confirms that the indirect ultrasonic method and respons surface methodology-based optimization are effective in improving the performance and character of water-in-biodiesel, potentially becoming a reference for the development of environmentally friendly renewable energy based on palm oil.
Performance Test of Methylene Blue Degradation Using TiO₂–Graphene Oxide Composite Synthesised from Coconut Shells Heltina, Desi; Fesya Putri, Andini; Fauziyah, Hidayatul; Peratenta Sembiring, Maria; Amri, Amun; Tao Jiang, Zhong
Rekayasa Vol. 23 No. 1 (2025)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v23i1.32529

Abstract

Industry produces textile liquid waste which contains dangerous compounds such as methylene blue which can damage the environment. One effective method to overcome this problem is to use a TiO2 nanocomposite-based photocatalyst modified with Graphene Oxide (GO). GO is obtained from the synthesis of coconut shells, which is a biomass waste. This research aims to synthesize and display the performance of a TiO2/Graphene Oxide composite photocatalyst from coconut shells in degrading methylene blue. The TiO2/Graphene oxide nanocomposite synthesis method begins by carbonizing coconut shells to form graphite. Carbonization removes volatile compounds and produces a rich carbon structure, which is the initial requirement for the formation of GO. Synthesis of GO from graphite using the Hummer method. Synthesis of TiO2/Graphene oxide composite using a solvothermal process with various GO mass ratios. The performance of the photocatalyst was tested for degradation using methylene blue. Analysis of the TiO2/Graphene Oxide Composite using XRD, FTIR, SEM, BET characterisation and UV-Vis Spectrophotometer. The results show that at GO of 15%, the composite showed the highest surface area and optimal anatase crystallinity, resulting in the best degradation efficiency (70%). Graphene Oxide is synthesized from coconut shell biomass waste. This research shows that the TiO₂–Graphene Oxide composite has high efficiency in degrading dangerous synthetic dyes from textile industry wastewater through an efficient photocatalytic mechanism. This composite application is an application of technology that contributes directly to achieving the Sustainable Development Goals (SDGs), especially SDG 6 (Clean Water and Adequate Sanitation), through the development of sustainable, efficient and environmentally friendly waste processing technology.
Sludge Filtration Installation Design for Wastewater Treatment in Industrial Areas Using Bar Screens, Sedimentation, and Silica Sand Filtration Methods Pita Rengga, Wara Dyah; Maulana, Dea; Widiastuti, Amelia Putri; Muna, Laili Nailil; Laksana, Mochamad Brian
Rekayasa Vol. 21 No. 2 (2023)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v21i2.32482

Abstract

Wastewater Treatment Plant is an important facility designed to process wastewater from various sources, such as households and industries, before it is discharged into the environment. The main purpose of WWTP is to eliminate or reduce contaminants in wastewater to meet the quality standards set by the government. The treatment process involves the screening stage of solid material, sludge sedimentation, and decomposition of biological or chemical contaminants. One of the main challenges in wastewater treatment is sludge carryover to the processing system, which can reduce pollutant parameters such as Biochemical Oxygen Demand, Chemical Oxygen Demand, Total Suspended Solids and ammonia. This study aims to design a sludge filtration system consisting of bar screening, sedimentation, and filtration unit with a combination of silica sand. The design is outlined in the form of a scientific article to contribute to the development of wastewater treatment studies. The bar screen is used to filter rough solids in the early stages, sedimentation is used to separate heavy particles using gravity, and the filtration unit is designed using a single silica sand filter to reduce TSS. With a processing discharge of 6,300 m³/day, the resulting design is expected to improve the operational performance of WWTPs, meet the wastewater quality standards according to PerMen LHK No. 16 of 2016, and produce good quality effluent BOD 13,43 mg/L, COD 40,47 mg/L, TSS 1,9 mg/L and ammonia 0,42 mg/L. The results of this planning provide a sustainable and efficient solution for wastewater treatment.
Design and Performance Evaluation of a Soybean Filtration Machine Utilizing an Electric Motor and Low-Torque Gearbox Nur Fatta, Muhammad Affa; Dwi Saputro, Danang; Hidayat, Hanif
Rekayasa Vol. 23 No. 1 (2025)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v23i1.19394

Abstract

The traditional soybean filtration process in small- and medium-scale tofu industries remains inefficient due to labour-intensive operations, inconsistent extract quality, and high processing time. Manual pressing methods often result in reduced extract yield, uneven texture, and contamination risks. Therefore, this study aims to design and evaluate a soybean filtration machine powered by an electric motor and a low-torque gearbox, with the goal of improving efficiency, hygiene, and mechanical reliability. The research employed a Research and Development approach using the Four-D model: define, design, develop, and disseminate. A 0.5 hp electric motor was integrated with a 1:20 ratio gearbox to achieve stable rotational motion for the reciprocating filter system. The mechanical analysis indicated a total working force of 613.725 N, a motor torque of 61.37 Nm, and an output torque of 1,105 Nm after accounting for efficiency. The system demonstrated low structural deflection (0.405 mm) and a high safety factor of 3.81, confirming robust mechanical integrity. Experimental testing yielded a filtration efficiency of 93% and an average flow rate of 1.2 L/min, showing a 70–80% reduction in processing time compared to manual filtration. The feasibility assessment resulted in an 88.63% approval rating from operators, classifying the machine as highly feasible. Overall, the designed system effectively improves productivity, ergonomics, and product consistency in soybean-based food processing.

Page 3 of 3 | Total Record : 28

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