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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,
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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 
Alternative Design of a Pneumatic Conveying Machine for Rice Husk as A Coal Substitute for Rotary Kiln Fuel in Cement Factories Permanadewi, Indrasukma; Febry Ibrahim, Ahmad; Azzahra Putri Solihin, Syifa; Aldiansyah, Rizky
Rekayasa Vol. 22 No. 2 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i1.18907

Abstract

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.
Sign Language Detection Application to Facilitate Communication for Speech and Hearing Impaired Individuals Based on Computer Vision Technology Using Inception Resnetv2 Arfriandi, Arief; Prabowo, Yoga Agung; Najuda, Moh Dafi; Puspita, Tri Anggi Ratna; Virnanda, Shakira Wahyu; Sunardiyo, Said
Rekayasa Vol. 20 No. 2 (2022)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v20i2.19433

Abstract

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.
Strategies for Clean Production in Methyl Isocyanate Synthesis for Pesticide Raw Materials Faisal, Deni; Sulaiman, Fatah; Pramudita, Marta
Rekayasa Vol. 21 No. 1 (2023)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v21i1.15782

Abstract

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.
Welding Automation Design using Metal Inert Gas for Straight and Circular Welding Suwandi Marwoto; Dwi Saputro, Danang; Karnowo, Karnowo; Maulana, Sonika
Rekayasa Vol. 22 No. 1 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i1.16187

Abstract

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.
Aerodynamic Performance Enhancement of Electric Vehicles Using Selig 1223 Airfoil Wing-Type Spoiler: A Computational Fluid Dynamics Study Fajar Rizqi Sandi Pratama; Aldias Bahatmaka; Amin, Muklis; Hyung, 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.v22i2.25166

Abstract

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 Ni’mahv, Latifatun; Catur Rini Widyastuti; Rahimsyah ljas Nur Rasyid
Rekayasa Vol. 20 No. 2 (2022)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v20i2.22426

Abstract

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
Seismic Interpretation Using RMS Amplitude and Envelope Attributes to Identify Hydrocarbon Prospects in the “CAT” Field, Central Sumatra Basin Sulaiman, Ryan; Adhi, M. Aryono; Nurcahya, Budi Eka
Rekayasa Vol. 21 No. 1 (2023)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v21i1.19597

Abstract

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.
A Simple Method in Evaluating the Performance of H2S Scrubber at Existing Biogas Plant Akbar, Ramavi; Hanif Ardhiansyah; Muhammad Wasim Ikram
Rekayasa Vol. 22 No. 2 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i2.30454

Abstract

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.
Site Classification Based on Shear Wave Velocity  from H/V Curve Inversion in Prambanan Subdistrict, Klaten Regency for Earthquake Risk Mitigation Rahma, Ilqia; Aryono Adhi, Mochamad; Budi Wibowo, Nugroho; Mustami' Limayukha, Desi; Fadlika Widyantari, Elsa; El Farsiyyi, Billqis; Sofyana Ulya, Rahmania
Rekayasa Vol. 21 No. 2 (2023)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v21i2.9863

Abstract

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.
Identification of Seismic Vulnerability  in Sleman Regency Based on Site Effect Analysis  Using Microtremor Data El Farsiyyi, Bilqis; Aryono Adhi, Mochamad; Budi Wibowo, Nugroho; Mustami' Limayukha, Desi; Fadlika Widyantari, Elsa; Rahma, Ilqia; Sofyana Ulya, Rahmania
Rekayasa Vol. 21 No. 2 (2023)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v21i2.9958

Abstract

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

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