Rekayasa : Jurnal Penerapan Teknologi dan Pembelajaran starting in 2024 migrates to better secure from various unwanted things, including journal hacking and so on. To submit, the author please visit the new website page of our journal at the link https://journal.unnes.ac.id/journals/rekayasa MIGRATION OFFICIAL STATEMENT HERE REKAYASA journal publishes exciting articles from all fields of research and Engineering Science. The journal's 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. REKAYASA Journal approaches practical research and aims to build a platform for Researchers and Academics for all critical aspects of Engineering and science The scope of REKAYASA Journal is to provide research media and essential references for the advancement and dissemination of research results that support high-level research in the fields of Engineering and Science. Original theoretical studies and application-based studies contribute to better understanding in all fields of Engineering and Science. REKAYASA Journal is accredited by the Ministry of Research, Technology and Higher Education of the Republic of Indonesia, Number: 158/E/KPT/2021 and achieved Sinta 3 which is valid up to Volume 22 Number 2 of 2024. The Accreditation Decree can be downloaded at the following link.
Analyzing the Total Resistance and Wave Pattern of Purse Seine Vessels with Photovoltaic-Powered
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.
Performance Test of Methylene Blue Degradation Using TiO₂–Graphene Oxide Composite Synthesised from Coconut Shells
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
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.
Optimization of Water-in-Biodiesel Emulsification of Palm Oil by Ultrasonic Method using Respons Surface Methodology
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.
A Simple Method in Evaluating the Performance of H2S Scrubber at Existing Biogas Plant
Biogas as one of the renewable energy sources contains hydrogen sulfide (H₂S) which causes equipment corrosion and gives negative impacts on the environment. To study some factors that affect the H2S removal efficiency, evaluation was done on the performance of existing H2S scrubber. For the case study, it was found that the existing scrubber performance did not reach the target (< 200 ppm-v H2S) with 1,450 Nm3 biogas/h and 2,550 ppm-v H2S inlet (-10 mbarg and 35oC). Scenarios were made by varying the design parameters of the H2S outlet scrubber (0 - 1,140 ppm-v), H2S inlet scrubber (2,550 and 3,000 ppm-v), and biogas flow (1,450 and 1,700 Nm3 biogas/h). Based on the analysis results, it was found that the initial design had already considered an overdesign factor of at least 52 times. Through solubility and residence time analysis, favorable scrubber operation is to run at low liquid spray flow (~ 70 m3/h). In addition, low flow liquid spray could help activate the bacteria on the bio-packing media surfaces so that they are not eroded by the high erosive spray velocity. This study’s results are expected to be a reference for the biogas industry in evaluating the performance of H2S scrubbers.
Copyright (c) 2024 Rekayasa : Jurnal Penerapan Teknologi dan Pembelajaran
Aerodynamic Performance Enhancement of Electric Vehicles Using Selig 1223 Airfoil Wing-Type Spoiler: A Computational Fluid Dynamics Study
The performance of electric vehicles (EVs) is significantly influenced by aerodynamic forces, which directly affect energy consumption and vehicle stability. One of the main challenges in this regard is the increase in lift and drag forces at higher speeds, which compromises efficiency and handling. This study investigates the impact of a wing type rear spoiler, designed using the Selig 1223 airfoil, on the aerodynamic behavior of EVs. A comparative computational fluid dynamics (CFD) simulation was conducted on two vehicle models: one without a spoiler and another equipped with the Selig 1223 spoiler mounted at a 15° angle of attack. Both models were tested under five speed conditions ranging from 40 to 120 km/h. The simulation results demonstrated a notable improvement in aerodynamic performance. The spoiler produced an average reduction in the lift coefficient (Cl) of approximately 110%, while the drag coefficient (Cd) showed only a slight increase, with the highest recorded rise being 13.3% at 120 km/h. Pressure distribution analysis revealed a substantial increase in static pressure at the rear of the vehicle (Point P3), rising from 37.47 Pa to 660.859 Pa, indicating enhanced downforce. Additionally, streamline and velocity contour plots confirmed improved airflow regulation and reduced turbulence behind the vehicle when the spoiler was installed. These findings indicate that the Selig 1223 airfoil spoiler effectively enhances EV stability and safety with minimal aerodynamic penalties, making it a promising aerodynamic enhancement for future electric vehicle designs.
Development and Verification of Potassium Determination Method in Solid NPK Fertilizer by Atomic Absorption Spectrophotometry
The measurement of potassium levels in solid NPK fertilizer using the K₂O digestion method still requires repeatability to ensure the validity of the measurement results. This study aims to develop and validate a method for determining potassium levels using the P₂O₅ digestion method in accordance with SNI 2803:2012, employing a pragmatic approach based on SNI 7763:2018. Potassium analysis was performed using an Atomic Absorption Spectrophotometer (AAS) with several validation parameters. The potassium levels measured using both the K₂O and P₂O₅ digestion methods were 14%. The method demonstrated linearity, with a correlation coefficient (r²) of 0.9986. The precision values for the K₂O and P₂O₅ digestion methods, based on Relative Standard Deviation (%RSD) < 2/3 CV Horwitz, were 1.6% < 1.8% and 1.1% < 1.8%, respectively, while t-calculated (0.646) < t-tabulated (2.179). Accuracy, as indicated by the percentage recovery for the K₂O and P₂O₅ digestion methods, was 108% and 101%, respectively. The P₂O₅ digestion method is categorized as an accurate, precise, and efficient technique for determining potassium levels in solid NPK fertilizer samples, particularly in large quantities
Copyright (c) 2022 Rekayasa : Jurnal Penerapan Teknologi dan Pembelajaran
Identification of Hydrocarbon Reservoir Distribution Using Seismic Attributes: RMS Amplitude and Sweetness in the Bani Field, South Sumatra Basin
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.
Copyright (c) 2023 Rekayasa : Jurnal Penerapan Teknologi dan Pembelajaran
Evaluation of Structural Features and Hydrocarbon Reservoir Potential of the Baturaja Formation Using Seismic Envelope and Sweetness Attributes
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.
Seismic Interpretation Using RMS Amplitude and Envelope Attributes to Identify Hydrocarbon Prospects in the “CAT” Field, Central Sumatra Basin
To enhance oil production rates, optimising idle wells with reserve potential and continuing exploration efforts to discover new hydrocarbon resources are necessary. The CAT Field in the Central Sumatra Basin is one of Indonesia's prospective oil and gas-producing areas. This study aims to identify and map the distribution of sandstone reservoirs through 3D seismic data interpretation using RMS Amplitude and Envelope seismic attributes. The data used are secondary data from a reflection seismic survey processed at the Energy Study Centre. The interpretation stages include well-to-seismic tie, horizon picking, time structure mapping, and seismic attribute analysis. The interpretation results show that RMS Amplitude values in the Duri Formation range from 0.80 to 5.60, while in the Bekasap Formation, they range from 0.00 to 4.00. The Envelope attribute values in the Duri Formation range from 0.60 to 8.40, and from 0.50 to 6.00 in the Bekasap Formation. High attribute value zones are consistently detected around wells CAT_01, CAT_03, and northwest of CAT_02, corresponding to elevated topography based on the time structure map. These findings indicate potential hydrocarbon accumulation in the area, making it a prime target for field development and revitalisation. Seismic attribute interpretation offers an efficient exploration approach and supports future sustainable exploration efforts.
Sign Language Detection Application to Facilitate Communication for Speech and Hearing Impaired Individuals Based on Computer Vision Technology Using Inception Resnetv2
Communication is a fundamental human need, yet not everyone possesses perfect communication abilities. People Communication is a fundamental human need, yet individuals with speech and hearing impairments face challenges due to the limited understanding of sign language among the general public. This study applies Artificial Intelligence and Computer Vision to enhance communication accessibility by detecting hand gestures and converting them into text. The lack of real-time sign language translation remains a barrier for individuals with disabilities. Existing systems often struggle with accuracy and device compatibility. This research develops and evaluates HARDISC, an Android-based application that recognizes letters A–Z through hand movement detection using a camera. The goal is to provide an effective and inclusive communication tool for the speech and hearing impaired. HARDISC utilizes Transfer Learning with Inception ResNetV2 and VGG16 for gesture classification. Image processing enables the camera to detect and translate hand movements into text. Model evaluation was based on accuracy, loss values, and device compatibility. Results show Inception ResNetV2 achieved 98.98% accuracy with a 0.0417 loss value, while VGG16 recorded 99.40% accuracy with a 0.0146 loss value, demonstrating high performance. HARDISC is compatible with Android KitKat 4 to Android 12, ensuring accessibility. This application provides an innovative, real-time solution to bridge communication gaps for individuals with speech and hearing impairments, improving their interaction with the general public.
Design and Performance Evaluation of a Soybean Filtration Machine Utilizing an Electric Motor and Low-Torque Gearbox
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.
Alternative Design of a Pneumatic Conveying Machine for Rice Husk as A Coal Substitute for Rotary Kiln Fuel in Cement Factories
The reduced amount of coal transported to cement factories is being diverted to rice husk, which is biomass, to facilitate the use of increasingly expensive coal. This transition is necessary due to the different characteristics of rice husk compared to coal. Additionally, the combustion process in rotary kilns requires extremely high temperatures (1,400–1,500°C). However, a significant portion of the generated energy is lost through the kiln walls, exhaust gases, and heat radiation. These heat losses reduce thermal efficiency and increase fuel consumption. Coal, fuel oil, and natural gas are the primary energy sources for cement kilns, which are not only expensive but also have negative environmental impacts. The fluctuation in fossil fuel prices further affects overall cement production costs. To address these challenges, cement factories must design an efficient rice husk conveying system from storage to the rotary kiln. Transporting rice husks with air ensures no unintended reactions while allowing smooth flow through closed horizontal and vertical transport pipes commonly used in the industry. This study aims to design a pneumatic conveying machine with a closed air pressure system to transport biomass (rice husks) at a capacity of 7 tons/hour as an alternative fuel for rotary kilns in the cement industry. The design method follows several stages, including practical work experience, literature review, material selection, design considerations, conceptual design, calculations, and technical drawings. The proposed system utilizes the dilute phase method, with a blower power of 49.26523 kW pushing the rice husks toward the hopper. The pipeline flow parameter, measured as the pressure drop, is 132.9673 kPa. The selected materials include galvanized iron pipes with two elbows to connect horizontal and vertical sections.
Evaluation of Effectiveness and Benefits of iRAP and Bina Marga Methods for Road Safety Assessment on the Karanglo-Bts. Kota Batu (Karang Ploso) Segment
According to Road Safety (2002), traffic accidents result from vehicles, humans, road environments, and their interactions. Addressing these issues is crucial for improving road safety, particularly for operational roads and those under maintenance, to prevent recurring accidents in the same locations. This study examines the effectiveness and benefits of two road safety assessment methods: the iRAP ranking analysis method and the Bina Marga ranking analysis method. The Karanglo–Batu City Border (Karang Ploso) road segment, spanning 7.99 km, was selected as the study area. Both methods analyze five key accident types: roadway departure, head-on collisions due to loss of control or overtaking, intersection accidents, and accidents at property access points. Factors influencing these accidents include probability, severity, operational speed, external traffic, and median traversability, with star ratings assigned based on the Star Rating Score (SRS). The iRAP method, utilizing the iRAP Demonstrator application, yielded an SRS score of 8.92 (3 stars), while the Bina Marga method, using manual calculations as per the Road Environment and Safety Guidelines Number 06/P/BM/2024, produced a score of 7.13 (3 stars). After implementing rehabilitation recommendations, both methods improved the score to 2.78 (4 stars). Effectiveness values were 35.68 for iRAP and 31.69 for Bina Marga, both categorized as effective. Post-improvement, the effectiveness value was 12.36, categorized as very effective. The iRAP method demonstrated higher direct benefits, particularly in data input, sampling, and implementation, making it more suitable for precise safety assessments.
Ultrafiltration Technology for Batik SME Wastewater Treatment: Column-Based Materials with Zippers for Plant Irrigation Water Supply
Textile batik wastewater discharged into drains can contaminate groundwater and harm ecosystems and human health. This study focuses on reducing hazardous heavy metals in sewage through physical and chemical filtration. Heavy metals in the wastewater can poison aquatic organisms, disrupt food chains, and contaminate water sources. The goal is to analyze the heavy metal content, pH, and colour of batik wastewater to make it safe for plant irrigation. The filtration process uses silica sand, activated carbon, and zeolite for mechanical filtration and ion exchange. Ultrafiltration is added to remove fine particles, heavy metals, and organic matter more effectively while resisting fouling. These materials are placed in zipper bags for easy replacement and regeneration. The wastewater passes through a filtration column consisting of two tanks: Tank 1 for fresh wastewater and sedimentation, and Tank 2 for overflow from Tank 1. Tests were conducted for Cr, Cu, Pb, and Zn using AAS, pH with a universal pH meter, and colour through organoleptic analysis. Cr levels initially exceeded quality standards, while Cu, Pb, and Zn were within safe limits. After filtration, reductions of Cr, Cu, Pb, and Zn were 81%, 8%, 22%, and 85%, respectively. The pH decreased from 10–11 to 7–8, and water color improved from murky greenish-brown to clearer. The results demonstrate the potential of ultrafiltration in reducing heavy metals, stabilizing pH, and improving water clarity. Wastewater treated through this process meets safety standards and can be used for plant irrigation.
Welding Automation Design using Metal Inert Gas for Straight and Circular Welding
An automatic welding machine is a tool used to carry out welding semi-automatically. The welding process is carried out using an Arduino as a microcontroller and a TB6560 driver as a Nema 23 stepper motor driver. Operation of the tool is carried out using Candle software. The tool movement system uses a lead screw and nut block on the Z axis as well as a timing belt and timing pulley to drive the X and Y axes. This machine has dimensions of 1200 mm long, 800 mm wide and 1250 mm high. The research model used is RnD. Tool testing is carried out by giving movement commands in the form of straight lines and circles to determine the accuracy of the movement, then testing is carried out using a welding machine to determine the welding results. Testing was carried out with variations of straight lines with variations of 18 mm, 24 mm, 25 mm, 30 mm, 36 mm, 42 mm, 50 mm, 75 mm, 100 mm, 125 mm and circle variations of 50 mm, 75 mm and 100 mm. Each variation was tested 3 times to produce an average backlash of 0.250 mm. Automatic welding machine can produce neat and even welds on straight welding, but there are still shortcomings in the results of circular and square welding. Adjustment of welding parameters and settings on the welding machine used needs to be done to improve the quality of the weld results.
Strategies for Clean Production in Methyl Isocyanate Synthesis for Pesticide Raw Materials
The increasing demand for pesticides in agriculture has led to a rise in the production of methyl isocyanate, a key intermediate in carbamate pesticide manufacturing. However, this process generates sodium sulfate as a by-product, dissolved in an aromatic solvent, which, if not adequately managed, contributes to environmental pollution and resource inefficiency. Chemical and environmental engineering are crucial in addressing this issue by developing effective separation and recovery methods. One potential solution is the distillation process, which separates sodium sulfate based on boiling point differences with water. However, the effectiveness of this method depends on operational conditions, particularly pressure and sulfuric acid concentration. This research focuses on optimising the recovery of sodium sulfate from methyl isocyanate production waste by investigating different operating pressures (atmospheric, vacuum, and combined) and sulfuric acid concentrations (0 M, 0.07 M, 0.15 M, 0.22 M, and 0.30 M). A recovery efficiency of sodium sulfate as high as 92.5% using vacuum distillation at a 0.22 M sulfuric acid concentration. Additionally, the condensate water contained 98.7% purity, making it suitable as a precursor for struvite fertiliser. Sodium sulfate is used as a raw material in producing insecticidal pesticides, with a purity level of 97.3%. This study demonstrates that an optimised distillation process can enhance the efficiency of pesticide production by minimising waste and maximising resource utilisation, contributing to cost efficiency and environmental in industrial pesticides.
Design and Construction of a Leisure Boat Bottom Glass Prototype as An Underwater Panorama Tourism Ride in Karimunjawa
The lack of proper tourism infrastructure often limits the potential of marine ecotourism. In Karimunjawa, coral reef tourism is a major attraction. However, accessibility remains an issue, especially for visitors who cannot swim or dive. This research focuses on the design and construction of a glass-bottom leisure boat prototype to provide a safe and immersive underwater panorama experience. This study falls within naval architecture and marine engineering, addressing the challenge of designing a stable, efficient, and safe tourism vessel. A key concern in ship design is balancing hydrodynamic efficiency with stability. While monohull boats are common, their transverse stability is relatively low. To overcome this, a catamaran hull configuration was chosen for better stability, larger deck space, and reduced resistance. The prototype was constructed with dimensions of 21.81 m in length, 2.63 m in height, and 7.51 m in width, featuring a glass-bottom viewing area to enhance the tourism experience. Hydrodynamic performance analysis showed an average increase in resistance of 12.39307 N as speed increased, demonstrating the vessel’s efficiency. The construction and testing process confirmed that the catamaran hull improves passenger safety, minimizes capsizing risk, and enhances the underwater viewing experience. This research contributes to sustainable marine tourism by introducing an innovative tourism ride that allows visitors to explore the underwater beauty of Karimunjawa without requiring diving skills. The successful design and construction of this prototype provide a model for future eco-aafriendly tourism vessels.
catamaran hull, hydrodynamic performance, marine ecotourism, naval architecture
Impact of Stroke Length Variation on Speed Efficiency in an Authomatic Tofu Extract Filtering Machine
In the tofu industry, especially at the home-scale "Tahu Pak Muhson," production remains largely manual, with traditional filtering methods. To enhance efficiency, a machine was designed to filter tofu juice, incorporating various crankshaft step lengths to optimize performance. This study aims to assess the impact of different step lengths on filtration time, tofu yield, and quality. Using a descriptive experimental research method with a quantitative approach, the independent variable is crankshaft stroke length (140, 200, 260 mm), while dependent variables include filtration time, yield, and tofu quality. The control variable is a consistent 10kg soybean input. Results indicate that a 260mm stroke length provided the quickest filtration, averaging 524.3 s, compared to 726 s for 140mm and 620 seconds for 200 mm. Yield for the 140mm stroke was 46%, 45.5% for 200mm, and 44.5% for 260 mm. Tofu quality showed minimal variation across different lengths, although the 260 mm stroke length produced tofu with a slightly coarser texture and a faster smell development. The findings demonstrate that step length impacts filtering efficiency and yield, with potential implications for tofu production scalability.
Optimizing Bio-Oil Yield from Pyrolysis of Spent Bleaching Earth for Liquid Fuel Production
Spent Bleaching Earth is an industrial waste generated primarily from vegetable oil processing and contains 20-40% oil by weight, which poses a fire hazard due to the risk of spontaneous combustion. Commonly, Spent Bleaching Earth is processed using extraction methods with solvents like n-hexane, methanol, or steam. However, transforming SBE into liquid fuel via pyrolysis remains underexplored. This research aims to convert into liquid fuel through pyrolysis. The process was conducted at 600 °C for 90 min, resulting in pyrolysis oil with a density of 992.8 kg/m³, a viscosity of 31.21 cSt, a calorific value of 40.63 MJ/kg, and a flash point of 36 °C. Additionally, the oil contained 21.18% phenol compounds. The remaining material from the process, including char, constituted 54% of the original spent bleaching earth mass. These results demonstrate the feasibility of using pyrolysis to convert into a valuable liquid fuel, offering a sustainable approach to manage this hazardous industrial waste while producing energy-rich byproducts. This study underscores the potential of pyrolysis as a waste-to-energy solution and a safer alternative to traditional disposal methods for Spent Bleaching Earth.
Site Effect Analysis in Prambanan District and Surroundings Using Shear Wave Velocity and Ellipticity Curve Method from Microtremor Data
The shear wave velocity (Vs) is a crucial parameter for determining subsurface layers by averaging the Vs value to a depth of 30 meters, known as Vs30. This study aims to analyze the subsurface soil layers, calculate the Vs30 value, and assess the potential seismic site classifications in Kapanewon Prambanan and its surrounding areas. The research utilizes secondary microtremor data from 27 observation points in the form of MSD files. The microtremor data was processed using Geopsy software with the HVSR method to generate an H/V curve. This curve was further analyzed with the Ellipticity Curve method via Dinver software to obtain the Vs profile at various depths. The findings suggest that the subsurface layers in Kapanewon Prambanan are predominantly composed of hard, very dense soil, soft rocks, and solid rocks, based on the Vs30 values. The Vs30 distribution across the region ranges from 267.857 m/s to 1675.977 m/s, classified into site categories A, B, C, and D. However, the majority of the area falls under site classes B and C. These classifications indicate that the regions under B and C have a relatively lower potential for significant earthquake wave amplification. Nonetheless, attention should still be given to areas categorized under sites D and E, particularly for earthquake disaster mitigation efforts. This detailed Vs30 analysis provides critical insights for seismic assessments, regional planning, and mitigation strategies in Kapanewon Prambanan.
Rahmania Sofyana Ulya Rahmania Sofyana Ulya
Desi Mustami Limayukha Desi Mustami Limayukha
Elsa Fadlika Widyantari Elsa Fadlika Widyantari
Evaluation of Seismic Vulnerability Index and Soil Classification in Sleman Regency Based on Microtremor Analysis and the HVSR Method
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.
Identification of Seismic Vulnerability in Sleman Regency Based on Site Effect Analysis Using Microtremor Data
Yogyakarta is a province in the southern part of Java Island which is close to volcanoes. In this area there are sedimentary materials, such as silt, sand, tuff, breccia, agglomerate and conglomerate so that they are at risk of being affected by local site effects when an earthquake occurs. This study aims to determine earthquake vulnerable zones in several areas in Sleman Regency, including Berbah, Kalasan and Prambanan Districts based on site effect analysis with dominant frequency parameters (f0), amplification factor (A0) and seismic vulnerability index (Kg) using micro seismic data with data of 27 points which are then processed using the Horizontal to Vertical Spectral Ratio (HVSR) method and micro zonation using Geographic Information System (GIS). The results of data processing show that the site class in Sleman Regency is divided into 3, namely SD (Medium Soil), SC (Very Dense Soil) and SB (Rock). Areas with rock formations with soft soil structures are the most vulnerable areas to earthquakes. The lowest
Seismic Vulnerability Microzonation Based on Dominant Frequency and Amplification Using the HVSR Method in Wedi, Changewaro (Klaten) and Gendangsari (Yogyakarta)
The Yogyakarta region is prone to frequent earthquakes, highlighting the need for seismic vulnerability assessment and micro zonation analysis. This study aimed to evaluate the area's seismic vulnerability by utilizing microtremor methods to estimate dominant frequency, amplification, seismic vulnerability index, and shear wave velocity. Microtremor points were analyzed using the Horizontal Vertical Spectral Ratio method, with data processed through Geopsy software to obtain f0, A0, and H/V curves. The H/V curve was further inverted using Dinver software to derive ellipticity curves, ground profiles, and Kg values. The results revealed that the dominant frequency values ranged from 0.668 Hz to 18.271 Hz, with higher values prevalent. The soil types in the area were classified as type IV and type I, primarily consisting of older, hard sandy rocks and gravels. Amplification values ranged from 1.03 to 8.36, indicating low amplification levels and placing the area in zone 1. Kg values varied from 0.066 to 15.07 s²/cm, suggesting moderate seismic vulnerability. If an earthquake occurs, the region would experience shaking, though damage would be moderate. Vs30 values ranged from 179.64 m/s to 681.82 m/s, categorizing the soil as hard, dense, soft, or medium.
Site Classification Based on Shear Wave Velocity from H/V Curve Inversion in Prambanan Subdistrict, Klaten Regency for Earthquake Risk Mitigation
One of the areas that has become a historical tourist attraction in Klaten Regency is Prambanan District. Prambanan District in the south is directly adjacent to Kapanewon Prambanan which has an Opak Fault. This study aims to microzonate earthquake-prone areas based on microseismic parameters using a portable seismograph at 27 measurement points. Data analysis was performed using the Horizontal to Vertical Spectral Ratio (HVSR) method and the ellipticity curve with the help of Geopsy and Dinver software. The results showed that the range of f0 values was between 0.9 and 18 Hz, which was predominantly included in the Type I classification. The A0 values were in the range of 1.2-4 with the size of the distribution of A0 being dominantly low. The value of Kg in this area is classified as low category with a range of 0.1-14. Prambanan District has vs30 values ranging from 234–1260 m/s which are classified into 3 sites namely B, C, and D. The results of this study indicate that Prambanan District has soil with a thick layer of sediment based on information on the distribution of shear wave velocity values to depth 30 meter. These results are relevant as an effort to mitigate earthquake disasters, especially in vulnerable areas such as Prambanan which has a history of seismic activity due to the presence of the Opak Fault.
Addition of Germicidal UV-C Radiation Equipment in the Sterilization Process to Extend the Shelf Life of Cow's Milk
Cow's milk provides essential human nutrients, including calcium, protein, and minerals. However, it is highly susceptible to bacterial contamination, which leads to rapid spoilage. Pasteurization is the most common method to process cow's milk, effectively reducing microbial levels. However, some heat-resistant bacteria can survive the pasteurization process, limiting its effectiveness in ensuring long-term milk safety. This study investigates the use of chemical engineering technology by combining pasteurization and UV-C radiation methods, either sequentially or simultaneously, to improve the effectiveness of milk sterilization. The use of combined techniques aims to leverage the strengths of both processes, achieving superior microbial reduction and extending milk shelf life. Different operating temperatures and radiation durations were tested to identify optimal processing conditions. The findings revealed that this combined approach achieved a significant bacterial reduction of 99.95%, decreasing the microbial count from an initial 1.9 × 10⁶ cfu/mL to 7.0 × 10² cfu/mL. Moreover, the shelf life of the milk was extended to five months, demonstrating the effectiveness of the hybrid method. The study also monitored the milk's acidity (pH) throughout the process, which remained within optimal conditions of 6.5 to 6.8. This indicates that the combined treatment does not compromise milk quality. Integrating pasteurization with germicidal UV-C radiation offers a promising alternative for milk sterilization, improving microbial control and significantly increasing the shelf life of cow's milk. The results suggest that this dual-method approach could be a valuable advancement in dairy processing, enhancing both safety and efficiency in the production and preservation of milk.
Compact Eyeshadow Preparations from Chiken Egg Shell and Rosella Flower Petals Extract (Hibiscus Sabdariffa L) as Natural Colorants and Preservatieves
Eyeshadow is used to give the eye dimension to look attractive, so the selection of eyeshadow materials needs to be considered to avoid side effects that can occur on the surface of the eyelids. Eyeshadow can be made from natural ingredients. One of the natural ingredients that can replace talcum chemicals is chicken eggshell powder because chicken eggshell powder contains a source of calcium that can nourish the skin. Rosella flower petal powder extract is also added as a natural colourant for manufacturing this compact eyeshadow powder. In addition to functioning as a colourant, Rosella flower petals contain anthocyanins and flavonoids, which have antioxidant and antibacterial properties. This study aims to determine the innovation process of chicken eggshell waste into Compact Powder Eyeshadow as decorative cosmetics by analyzing the feasibility of eyeshadow through organoleptic tests, pH tests, particle uniformity tests, specific gravity tests, and water content tests. This study's results show that formula III's physical quality with an extract concentration of 50% has good physical quality compared to other concentrations because the resulting colour is light. However, the colour resistance produced is the same as other formulas and does not last long.
Sustainable Dyeing: Utilizing Natural Ketapang Colors for Shibori Products
The use of synthetic dyes in the textile industry produces wastewater with high potential for environmental pollution. Utilizing natural dyes from Ketapang leaves offers an alternative for reducing such wastewater and can be considered a sustainable dyeing method. According to data from the UNNES Conservation Development Agency, there are 5,170 Ketapang trees around the UNNES campus, indicating a plentiful supply for natural dye production. The purpose of this study is to explore the potential of Ketapang leaf dye in enhancing the aesthetic quality of Shibori products, specifically in terms of motif aesthetics and color direction. The research employs a quantitative approach with an experimental design, using a single variable. Data analysis was conducted through descriptive percentage statistics. The Shibori with the highest aesthetic value was produced using lime as a fixative, achieving a 95% rating (highly quality). Color direction analysis showed that each fixative produced different color outcomes: lime resulted in a Dijon color, alum produced a Corn color, and ferrous sulfate yielded a Seaweed color. Based on these findings, it can be concluded that natural dyes from Ketapang leaves contribute significantly to both motif aesthetics and color direction in Shibori dyeing, offering a sustainable and environmentally friendly alternative for textile production.