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Semesta Teknika
Published by Universitas Muhammadiyah Yogyakarta
ISSN : 1411061X     EISSN : 25025481     DOI : https://doi.org/10.18196/st
Core Subject : Engineering,
Engineering
SEMESTA TEKNIKA is a reputable refereed journal devoted to the publication and dissemination of basic and applied research in engineering. SEMESTA TEKNIKA is a forum for publishing high quality papers and references in engineering science and technology. The Journal is published by the Faculty of Engineering, Universitas Muhammadiyah Yogyakarta, INDONESIA. Copyright is by the publisher and the authors. The Journal is issued in electronic form and also issued in printed form as annual volume for the contributors only. The journal contains original research papers, review articles, short notes and letters to the editors. The topics of interest include modeling, experimental, analytical and numerical investigations on the mechanical, physical, chemical and mineralogical properties of material, developing the prototype/instrument, technology and construction process. Topic of management in industry and civil construction is also considered. SEMESTA TEKNIKA receives manuscripts from the contributor written in the Indonesian and English. Manuscripts submitted to the journal for publication must not have been previously published or is under consideration simultaneously by any other publication. Manuscripts submitted to SEMESTA TEKNIKA will be reviewed Peer Reviewers local and foreign.
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Articles 715 Documents
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Pengaruh Sudut Water Sprayer Dan Tekanan Air Dalam Sprayer Pump Terhadap Hasil Serbuk Alumunium Pada Proses Atomisasi Air Nur Rahman, Muhammad Budi; Suwanda, Totok
Jurnal Semesta Teknika Vol 9, No 2 (2006): NOVEMBER 2006
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Abstract

Metalurgi serbuk merupakan metode pembuatan benda-benda logam dengan menggunakan serbuk logam sebagai bahan dasar. Proses dalam teknologi metalurgi serbuk terdiri dari pembentukan serbuk, compacting, sintering dan finishing. Salah satu metode dalam pembuatan serbuk logam adalah dengan metode atomisasi air. Pembuatan serbuk dengan metode atomisasi air terdapat beberapa faktor yang mempengaruhi antara lain: sudut α (sudut tumbukan antara melting dengan butir air) dan tekanan air saat tumbukan. Penelitian ini bertujuan untuk mengetahui pengaruh sudut α, dan tekanan air terhadap optimalisasi hasil pembuatan serbuk dengan metode atomisasi air dan bentuk serbuk yang diamati dengan foto mikro. Proses pembuatan serbuk menggunakan metode atomisasi air dengan variabel bebasnya adalah sudut α yang ditentukan 30o, 40o, 50o dan 60o dan variasi tekanan air,  yaitu 25 kg/cm2, 30 kg/cm2, 35 kg/cm2 dan 40 kg/cm2. Bahan yang digunakan dalam proses atomisasi air adalah alumunium. Dalam penelitian ini diperoleh hasil bahwa sudut α dan tekanan tumbukan air pada melting mempengaruhi hasil produksi serbuk dengan metode atomisasi air. Hasil penelitian dengan variasi sudut α  diperoleh bahwa sudut  α = 30o menghasilkan produk 2,7%, sudut  α = 40o menghasilkan produk 4,05%, sudut α = 50o menghasilkan produk 3,23%, sudut α = 60o menghasilkan produk 1,8%. Penelitian dengan variasi tekanan air pada tekanan 20kg/cm2 tidak diperoleh serbuk, 25 kg/cm2diperoleh 2,9%, tekanan 30 kg/cm2 diperoleh 3,2%, tekanan 35kg/cm2 diperoleh 4,5% dan tekanan 40kg/cm2 diperoleh 2,9%. Hasil serbuk alumunium optimum secara teoritis dihasilkan pada sudut α 42,50 dan tekanan air 33,17 kg/cm2. Bentuk serbuk hasil proses atomisasi air sebagian besar adalah irregular, accicular dan flake.
Analisis Korosi pada Sambungan Double Nipple Pompa Submersible di Universitas Muhammadiyah Yogyakarta M. Al Aththar, Bambang Riyanta ,
Jurnal Semesta Teknika Vol 14, No 1 (2011): MEI 2011
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Corrosion is the deterioration of metal or alloy due to electrochemical reactions with its surroundings. The current study was conducted to determine the types and causes of corrosion on the double nipple connection of submersible pump which is used to pump water flooding the generator room at Universitas Muhammadiyah Yogyakarta. Chemical composition test was conducted to determine the material characteristics. The type of corrosion was determined by visual observation and confirmed with microstructure test. Chemical composition test was also conducted to investigate the nipple surface whether it has already been corroded or not. The water flooding into the generator room was analyzed to dete4rmine its chemical composition. The result shows that the material of the nipple is dead mild steel consisting of 0.133% carbon. Selective corrosion occurs on the outersurface of the nipple destroying 96.6% of its galvanized coating, and further shifted into a bimetal corrosion which attack 0.14 mm or 5.1% of the nipple wall thickness. Differential aeration corrosion attacked the inner surface of the nipple wall, due to the presence of Cl which is observed in the flooding water.
Pengaruh Penggunaan Abu Sekam Padi sebagai Bahan Pengisi pada Campuran Hot Rolled Asphalt terhadap Sifat Uji Marshall Rosyidi, Sri P. Atmaja
Jurnal Semesta Teknika Vol 15, No 2 (2012): NOVEMBER 2012
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Rice Husk Ash (RHA) has fairly high content of SiO2 and easily obtainable. It is inexpensive since it is the residual waste of the tile or brick combustion process that is not utilized properly. RHA has the potential to be used as filler in Hot Rolled Asphalt (HRA) since it has high flexibility mixture design. The influential characteristic of RHA is that it has fine aggregate fraction. This study aims to discover the physical properties of RHA, the characteristic of the Marshall test properties, the optimum bitumen content, and the economical comparison between the RHA-mixed HRA and the conventional one using stone dust filler. The results of this study indicate that the use of the RHA is able to increase the optimum bitumen content. In terms of economical comparison, the use of RHA as filler material is much more economical than using stone dust as filler.
Implementasi Mikrokontroler Sebagai Pengendali Kapasitor Untuk Perbaikan Faktor Daya Otomatis pada Jaringan Listrik Prasetya, Dana Bagus
Jurnal Semesta Teknika Vol 13, No 2 (2010): NOVEMBER 2010
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With increasing electricity rates, the demands of efficiency in electric power consumption is a major consideration. Efficient use of electric power is affected by many factors. Among them is the quality of electric power. Power quality is strongly influenced by the use of certain types of expenses that resulted in the decline of efficiency. In the distribution of electric energy there are several problem sencountered include the voltage drop, low cos Φ, and the loss of power. Load on the network load distribution can be either capacitive or inductive, but in general is an inductive load. If the inductive reactive load the higher the voltage drop will produce a zoom in, zoom power loss, cos Φ lower and lower distribution of power capacity. To reduce the inductive reactive power load required capacitive reactive power sources, one of which is to be installed in parallel capacitors. In this study will be designing and manufacturing tools for controlling capacitor banks according to cos φ m, so that power quality will be better. From the results of this research tool was able to detect the value of voltage, current,and cos φ. The resulting values of the three sensors is quite good. This tool is able tocontrol the capacitor bank in accordance with the value of cos φ meters.
Pengaruh Diameter Katoda pada Sensitivitas Pengukuran Gradien Kecepatan dengan Metode Polarografi Sukamta, Sukamta
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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Wall velocity gradient measurement using polarography gives very accurate output due to the absence of problem in fluid flow. Therefore this experiment is highly recommended. Based on the polarogram resulted in the polarography method, the potential that has to be applied to both electrode is 0.25 – 0.75 Volt, whilst in the experiment 0.45 is applied. Calibration has been done to single phase flow, by measuring as a result of  by friction between wall and current flow through electrode at constant flow rate. The ΔP data are used to determine τ. Relation plot between τ (resulted from ΔP measurement) and current can be obtained from the data acquisition device. The result of this research shows that the value of wall shear stress (as velocity gradient) is influenced by the increase of flow rate. Whilst measurement of wall shear stress shows that the cathode area gives effect on the sensitivity of the measurement,  a small cathode results in better shear stress data measurement (more sensitive). In this research the best wall shear stress was resulted in cathode with diameter d=0.2 mm.
Perancangan Perangkat Lunak untuk Ekstraksi Ciri dan Klasifikasi Pola Batik Soesanti, Indah
Semesta Teknika Vol 17, No 2 (2014): NOVEMBER 2014
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The popularity of batik patterns in Indonesia has varied. Industrial modern devices in imaging have supported batik pattern recognition and classification. The important of product pattern information could not naturally visible. The information about batik pattern can be achieved by using the appropriate software design of image processing for extracting the features. One of the potential procedures is the unsupervised classification method based on specific feature.  In this research, the specific feature extraction based on the eigenimage of batik pattern was done. In the final step, the nearest distance eigenimage between reference batik image and test batik image was used to identify the batik from the classical pattern field point of view. The results of batik image identification conformed 96.67% with the reference batik images.
Perubahan Kecepatan Aliran Sungai Akibat Perubahan Pelurusan Sungai Suyanto, Irham
Jurnal Semesta Teknika Vol 10, No 1 (2007): MEI 2007
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Jaringan syaraf tiruan merupakan salah satu topik baru yang menarik untuk dikaji dikarenakan mampu menangani permasalahan yang sangat kompleks.  Salah satu variabel yang berperan pokok untuk menghasilkan unjukkerja jaringan syaraf tiruan yaitu pemilihan parameter  fungsi aktifasinya. Tulisan ini mencoba menganalisis pengaruh fungsi aktivasi terhadap unjukkerja jaringan syaraf tiruan terutama parameter kemiringannya. Sebagai studi kasus dalam penelitian ini yaitu sejauh mana jaringan syaraf tiruan mampu mengenali pola karakter tulisan tangan. Pola karakter yang akan dicoba untuk dikenali yaitu karakter angka (dari 0 sampai 9). Permasalahan yang dihadapi dalam pengenalan pola tulisan tangan sangat kompleks, antara lain bervariasinya model tulisan tangan, pena untuk menulis, dan ukuran tulisan tangan. Didapatkan kesimpulan bahwa parameter kemiringan fungsi aktivasi untuk menghasilkan unjukkerja pengenalan terbaik didapatkan pada nilai kemiringan  0,8 dengan menggunakan sigmoid bipolar
Beton Mutu Tinggi dengan Admixture Superplastisizer dan Aditif Silicafume Pujianto, As’at
Jurnal Semesta Teknika Vol 14, No 2 (2011): NOVEMBER 2011
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Increasing concrete strength is one of the main necessities of concrete technology. For more than the last 20 years, high strength concretes with compressive strength ranging from 50 MPa up to 140 MPa have been used worldwide in high rise buildings and bridges with long spans, or buildings in aggressive environments. But in Indonesia high strength concretes possesses maximum compressive strength of 60 MPa. The properties of concrete are affected by cementitious matrix, aggregate, and the transition zone between these two phases. Reducing the water-cement ratio and the addition of pozzolanic admixtures like fly-ash are often used to modify the microstructure of the matrix and to optimise the transition zone. The reduction of the water-cement ratio results in a decrease in porosity and refinement of capillary pores in matrix, but flowing ability of the concrete will also decrease so that it can’t be workable. Then it workablity can be improve by the use of a superplastisizer. The method used refers to the planning of normal concrete, which is contained in the SK-SNI 03-2834-1992. The results showed that superplastisizer with doses of more than 2% of the cement paste does not increase the flowing ability of the paste anymore. For all the rest of the experiments, the superplastisizer dosage was determined about 2 % of the powder mass. The first tests showed a good workability of the fresh concrete and a good self compacting ability with the silicafume dosage of 10 % of the powder mass. The interest in reducing costs for increasing the concrete strength, can be successfully achieved in this research.
Perancangan Fondasi Pada Tanah Timbunan Sampah (Studi Kasus Di Tempat Pembuangan Akhir Sampah Piyungan, Yogyakarta) Widianti, Anita; Wahyudi, Dedi; Diana, Willis
Semesta Teknika Vol 8, No 1 (2005): MEI 2005
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Tempat Pembuangan Akhir Sampah (TPAS) merupakan kebutuhan setiap daerah guna mengatasi masalah sampah. Apakah lahan yang sangat luas tersebut  nantinya dapat dimanfaatkan kembali ? Berdasarkan pertanyaan itulah penelitian ini dilakukan. Tujuan dari penelitian ini adalah untuk merancang fondasi berdasarkan daya dukung tanah yang mampu menahan beban dan penurunan yang tidak berlebihan dari hasil uji sondir di lapangan.Penelitian dilakukan di zona pertama dari TPAS Piyungan, Yogykarta  yang merupakan zona di mana proses penimbunan dan pemadatannya telah selesai.  Hasil uji sondir pada dua titik digunakan sebagai dasar untuk merancang fondasi dari struktur bangunan dua lantai, dengan mengacu pada Standar Tata Cara Perhitungan Struktur Beton Untuk Bangunan Gedung, SK SNI-T-15-1991-03.Dari hasil analisis menunjukkan bahwa fondasi telapak dapat digunakan dengan kedalaman 1,6 m. Fondasi tersebut  dirancang berukuran 100 cm x 100 cm dengan ketebalan 25 cm, jumlah tulangan sebanyak 8 buah dengan diameter 10 mm dan spasi tulangan 12 cm. 
Peningkatan Efisiensi Kompor LPG Dengan Menggunakan Reflektor Radiasi Panas Bersirip Sudarno, Sudarno; Fadelan, Fadelan
Semesta Teknika Vol 18, No 1 (2015): MEI 2015
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Heat wasted due to radiation from the flame around the LPG stovecan lower stove efficiency. The wasted heat would be exploited by using a finned heat reflector . The working principle of this tool is to capture the wasted heat  and reflect to the load so that it becomes useful energy . Preliminary data indicate that areflector without fins can increase stove efficiency., The objective of this research isto determine the performace finned heat reflectorin increasing LPG stove  efficiency. A piece of stainless steel plate as a truncated cone-shaped finned experimental model was used as a reflector. The efficiency test is done through  boiling water test. The number of fin of the the same dimensions were varied, starting from one-line to three-line fins. The performance of the stoves using reflectorwith fins were compared with that of stove using reflector without finsand with that of stove without reflectot. Based on test results, it is found that the use of finned reflectors is able to increase the efficiency of LPG stoves. The highest efficiency is obtained on the use of reflectors with three rows of fins, which amounted to 44.09%. The magnitude of the increase is compared to without using a reflector at 5.22%, while compared with the reflector without fins for 5.01%. Based on the test of temperature distribution is obtained also that the use of reflector finned heat radiation can increase the area of complete combustion.

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