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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 5 Documents
 1 
Search results for , issue "Vol. 22 No. 1 (2024)" : 5 Documents clear
Addition of Germicidal UV-C Radiation Equipment in the Sterilization Process to Extend the Shelf Life of Cow's Milk Wulansarie, Ria; Rusiyanto, Rusiyanto; Dino Alfian, Rangga; Diyah Ayu Utami, Kiki; Rahmah, Ladunia; Izza Arinanda, Miftakhul; Dyah Pita Rengga, Wara
Rekayasa Vol. 22 No. 1 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i1.6239

Abstract

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.
Optimizing Bio-Oil Yield from Pyrolysis of Spent Bleaching Earth for Liquid Fuel Production Okzani, Syahrial; Said, Muhammad; Bahrin, David
Rekayasa Vol. 22 No. 1 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v20i2.10398

Abstract

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.
Design and Construction of a Leisure Boat Bottom Glass Prototype as An Underwater Panorama Tourism Ride in Karimunjawa Aryadi, Widya; Bahatmaka, Aldias; Karnowo, Karnowo; Rumondang, Juwita Ria; Rumapea, Fedrik Immanuel; Kurniawan, Ahmad Khusom; Kusuma, Anwar Widjaya; Hidayat, Indra Nurul
Rekayasa Vol. 22 No. 1 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i1.13881

Abstract

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.
Evaluation of Effectiveness and Benefits of iRAP and Bina Marga Methods for Road Safety Assessment on the Karanglo-Bts. Kota Batu (Karang Ploso) Segment Devayanti, Shafira; Machsus, Machsus; Khoiri, Mohamad
Rekayasa Vol. 22 No. 1 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i1.18056

Abstract

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.
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.

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