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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 5 Documents
 1 
Search results for , issue "Vol. 20 No. 2 (2022)" : 5 Documents clear
Compact Eyeshadow Preparations from Chiken Egg Shell and Rosella Flower Petals Extract (Hibiscus Sabdariffa L) as Natural Colorants and Preservatieves Agustin, Eny Widhia; Wara Dyah Pita Rengga
Rekayasa Vol. 20 No. 2 (2022)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v20i2.2935

Abstract

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.
Seismic Vulnerability Microzonation Based on Dominant Frequency and Amplification Using the HVSR Method in Wedi, Changewaro (Klaten) and Gendangsari (Yogyakarta) Desi Mustami Limayukha, Desi Mustami Limayukha; Adhi, Mochamad Aryono Adhi; Wibowo, Nugroho Budi; Bilqis El Farsiyyi, Billqis El Farsiyyi; Elsa Fadlika Widyantari, Elsa Fadlika Widyantari; Ilqia Rahma, Ilqia Rahma; Rahmania Sofyana Ulya, Rahmania Sofyana Ulya
Rekayasa Vol. 20 No. 2 (2022)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v20i2.9957

Abstract

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.
Impact of Stroke Length Variation on Speed Efficiency in an Authomatic Tofu Extract Filtering Machine Saputro, Danang Dwi; Pangestu, Wahyu Dwi
Rekayasa Vol. 20 No. 2 (2022)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v20i2.11941

Abstract

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.
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.
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

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