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Semesta Teknika
ISSN : 1411061X     EISSN : 25025481     DOI : https://doi.org/10.18196/st
Core Subject : 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 659 Documents
Penyusunan Model Elemen Hingga Interaksi Persamaan Aliran dengan Persamaan Sebaran Udara Adam Pamudji Rahardjo, Jazaul Ikhsan ,
Jurnal Semesta Teknika Vol 15, No 1 (2012): MEI 2012
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Aeration process is one of water treatment processes. The process consists of two physical phenomena, flow, and spreading of air bubble. This research has developed a finite element model for three-dimensional flow and spreading of air bubble. The flow equation employs Navier-Stokes equation. The spreading of air bubble is modeled as convection-diffusion equation. The Navier-Stokes and the spreading of air bubble equation are combined by Navier-Stokes equation with additional new term, which shows the accelerated flow caused by the air bubble moves. The Navier-Stokes equation was solved in four stages, i.e., Taylor Galerkin convection approximation, viscous prediction, pressure correction and velocity correction stages. Galerkin Standard method was used to solve the spreading of air bubble equation. Quadratic brick finite elements with 20 nodes were used on the geometry. To show performance model, comparison to the result of air bubble investigation was carried out. The numerical model that has been obtained is capable of simulating the phenomena of air bubble spreading and flow. The numerical stability analyses showed that the numerical scheme of convection and diffusion equation based on Galerkin is stable for Courant Number £ 0.01 and Peclet Number <125.
Kajian Komprehensif Pengaruh Perlakuan Alkali Terhadap Kekuatan Komposit Berpenguat Serat Nanas-Nanasan (Bromeliaceae) Suwanda, Totok; Nuri, Sigit Hidayat; Diharjo, Kuncoro
Jurnal Semesta Teknika Vol 9, No 2 (2006): NOVEMBER 2006
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Penelitian ini bertujuan untuk menyelidiki pengaruh perlakuan alkali (5% NaOH) terhadap sifat tarik (tegangan, regangan, modulus elastisitas) bahan komposit berpenguat serat nanas-nanasan (bromiliaceae) dengan matrik unsaturated polyester. Karakteristik penampang patahan diselidiki dengan pengamatan menggunakan foto makro. Bahan utama penelitian adalah serat nanas-nanasan kontinyu, NaOH, dan resin unsaturated polyester. Serat yang digunakan dikenai perlakuan alkali (5% NaOH) selama 0, 2, 4, 6, dan 8 jam. Pembuatan komposit dengan metode cetak tekan pada kisaran fraksi massa serat 15% - 50. Pembuatan spesimen uji komposit dan prosedur pengujiannya mengacu pada standar ASTM D 638. Hasil penelitian menunjukkan bahwa perlakuan alkali (5% NaOH) mampu menghilangkan lapisan seperti lilin di permukaan serat sehingga serat dan resin memiliki ikatan (mechanical bonding) yang kuat. Komposit yang diperkuat serat yang dikenai perlakuan alkali memiliki kekuatan yang lebih tinggi dibandingkan dengan komposit yang diperkuat serat tanpa perlakuan.  Semakin tinggi fraksi massa serat (Wf)  maka kekuatan tariknya juga semakin besar. Pada di atas 30%, kekuatan tarik paling besar terjadi pada komposit yang diperkuat serat dengan perendaman alkali selama 4 jam, dan selanjutnya disusul oleh komposit yang diperkuat serat dengan perendaman alkali selama 2 jam pada (Wf). Komposit yang diperkuat serat perlakuan alkali selama 4 dan 2 jam juga memiliki modulus elastisitas yang lebih tinggi, yaitu masing-masing 40.71 GPa dan 50.65 GPa pada Wf sekitar 38%. Jenis patahan splitting in multiple area terjadi pada komposit yang diperkuat serat dengan perlakuan NaOH selama 4 jam, 2 jam, dan tanpa perlakuan. Namun, komposit yang diperkuat serat dengan perlakuan NaOH selama 8 jam memiliki jenis patahan patah tunggal. Berhubung penampang patahan komposit yang diperkuat serat tanpa perlakuan mempunyai mekanisme kegagalan fiber full out, maka kekuatan komposit ini pun menjadi rendah karena memiliki ikatan antara serat dan matrik yang lemah.
Analisa Kegagalan Sambungan Las Pada Tiang Penyangga Dermaga Syahputra, Koko Nusyi; Nugroho, Aris Widyo
Semesta Teknika Vol 18, No 1 (2015): MEI 2015
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Welded join failure analysis of broken jetty head strut has been carried out to find out the root cause of the failure which was obverved at the ring welding. Specimens being made of unbroken and broken struts were characterized and analyzed. The results show that the chemical composition of the based metal and the strut welded  joins especially their phosporus content were close to that of the ASTM A 252 grade 2 standard.   A common phenomenon was noted on the hardness testing result where the hardness numbers of the weld metal zone were found being higher than those of the base metal. The Widmanstatens stucture was noticed on both the weld metal and the coarse grain zone.  Further examination of the macrostructures revealed that blow holes and incomplete fusions were detected on the weld metal of the broken struts.  These flaws may the root cause of the failure because they acted as an initial crack that may propagate until fracture.
Aplikasi Metode Nilai Hasil (Earned Value Method) pada Sistem Pengendalian Proyek Pujihastuti, Siti Yuliani; Priyo, Mandiyo
Jurnal Semesta Teknika Vol 15, No 2 (2012): NOVEMBER 2012
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In a project implementation, the project implementer wants the project completed on time as efficient as possible while the produced quality is in accordance with the initial plan. Therefore, in order to meet the requirements for controlling process and to minimize any deviations that can occur during the project, the earned value method is considered accurate. The aim of this study was to identify the final result of the project which will be achieved in the aspect of cost (whether the project experience gains, losses, or within budget) and time (whether the project is delayed, ended early, or on time as scheduled). The study was conducted on the 4th, 8th, 12th, 16th, and 20th weeks by using the earned value. Earned Value Method, or often called the Concept of Earned Value, is the concept of calculating project costs in accordance with the budget and the scope of job which have been completed or implemented (budgeted cost of works performed). This method combines the cost, schedule, and work performance of a project. Therefore, this method is considered effective in monitoring and controlling project activities.
Extensive Geotechnical Instrumentation Program to Control Dike Raising Constructed on Soft Clay Tabbal, Mahmoud; Mansour, Ziad
Jurnal Semesta Teknika Vol 12, No 2 (2009): NOVEMBER 2009
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In its quest of increasing potash production, Arab Potash Company (APC) decided to increase the size of their salt evaporation pans. The Dike 18 which is spanning a length of 13km and enclosing a pan area of 16.5km2 was built between January 1996 and December 1997 as part of APCs expansion scheme. The foundation soils were predominantly varies from soft to very soft silty clay. From laboratory and field test results the undrained shear strength of the clay was between 28 to 40 kPa. An extensive instrumentation program was designed and implemented in order to control the dike raising during construction as well as to monitor the performance of the dike foundation during and after the construction. Instrumentations being installed included settlement spider magnets, level stations, standpipe and pneumatic piezometers. The major constraints of the instrumentation program were the large vertical settlements (2-3m) of the very soft clays, artesian conditions where sand and salt layers were present, high salinity of the groundwater and the development of sinkholes. Special installation and protection measures were developed to overcome these constraints. The performance aspects of the instruments were discussed and typical plots were presented. 
Pengaruh Pemodelan Kotak Resapan Buatan di Saluran Drainase terhadap Debit Limpasan Adinda, Sabarani; Barid, Burhan
Jurnal Semesta Teknika Vol 17, No 1 (2014): MEI 2014
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Drainage isasewer system in an areathat serves todrain excess rainfall. Initially, an artificial drainage channel could absorb water because the drainage channel is made from landorland with grass. Negative impacts frequently occurrence on the channel walls that are eroded by water see page. While the current drainage channel is impermeable, making direct runoff flows rapidly into water bodies. Land use is increasingly impermeable resulting bigger runoff and causing negative impacts, such as floods and decreasing groundwater savings due to rainfall directly flows into water bodies orriver nearby. In this paper, authortried tomake adrainage channel innovation by making boxes infiltration along the concrete channel. The aim of the study is to determine the effect of artificial recharge box modeling along drainage channels in reducing runoff using wastel and and grintinggrass(Cynodondactylon) media, determine the ratio of absorptionability between box wastel and media and Grinting grassmedia in reducing runoff using concrete channel/watertight as a reference. The model is made of wood with the size of 750×30×20cm and 5catchment box made every distance of 100cm along the channel, then the water flowed into the channel for an hour, and velocity data taken every five minutes before and after the flow through the box and also water level data taken every five minutes. The result shows that artificial recharge box with wasteland media can reduce runoff entering the channel, with the ability to reduce runoff at first hour about of 38.322% and it will decrease every hour, on it is smallest on the fourth hour 4 about of 28.038%. Also, a model with grintinggrass media can reduce runoff and the largestefficiency value is about 49.744% in first hour. Channel modeling with artificial recharges box using grinting grass media is better than only using wasteland for reducing.
Pemilihan Mesin Welding Otomatis Dengan Penerapan Value Engineering Dan Analitical Hierarchy Process Nuruddin, Moch; Andesta, Deny
Jurnal Semesta Teknika Vol 11, No 1 (2008): MEI 2008
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By chosening machine of welding automatic with Value Engineering, hence company can know which machine is which have high value and can improve production process specially to part of welding. With quality, quality of product which different each other hence consumer have to be clever in assessing and chosening reliable product. Because many company promoting its product with advertisements, so that make consumer interest to buying. This research aim to look for and analyse some alternative which can be made size measure in chosening machine of welding reliable automatic. Election of merk here there is three merk type for example Panasonic, Daihen, and Hitachi. From third this merk type will be selected which merk which have best quality. Result of got calculation, hence machine merk the selected is merk of Hitachi because this machine have high value and difference is expense of Rp 35 million compared to two other alternative. this Volts machine Pri equal to 380V, input pri 42,5KVA 23,5KW and current output 500A. If compared to this machine alternatives have value of Vn equal to 2,1.
Perbaikan Sifat Mekanis Batu Bata Tanpa Dibakar dengan Campuran Limbah Karbit dan Abu Sekam Padi Andre, Yosi; Siagian, Taufik Nugraha
Jurnal Semesta Teknika Vol 13, No 1 (2010): MEI 2010
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Brick is one important element in a building. Bricks are generally made by burning dry clay , and this process will emit air pollutant. In addition, the bricks that widely available on the market have a poor quality. Therefore, the quality of bricks needs to be effectively improved by means of environmentally friendly and low cost procedure. This research aims to improve the mechanical characteristics of unburnt bricks by adding a mixture of calcium carbide residue (CCR) and rice husk ash (RHA). In this study, the effect of the percentage of additive material and the proportions of CCR and RHA on the mechanical properties are studied. The results showed that the compressive strength of bricks is influenced by the content of additive material. In addition, the optimum compressive strength was found to be after 21 days of cating for all additive material, afterwhich the strength sarted to decrease. Bricks possessing the highest compressive strength are those produced with 70% additive and CCR-to-RHA ratio of 2/1. The compressive strength reached 125.91 kg/cm2 after 21 days of moulding.
Perbandingan Kekerasan dan Kekuatan Tekan Paduan Cu – Sn 6% Hasil Proses Metalurgi Serbuk dan Sand Casting Ramdani, Deny Fajrur; Rahman, Muh Budi Nur; Suwanda, Totok
Semesta Teknika Vol 11, No 2 (2008): NOVEMBER 2008
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Metal production by sand casting and powder metallurgy indicates the advantage of metal process technology. Bearing materials must have hardness and compressive strength properties to withstand wear and pressure load. Material porosity provides the space for lubricant. The lubrication will decrease the friction and keep temperature low. Low friction and low temperature will increase the life time of bearing. The goal of this research is to compare the hardness, compressive strength, macrostructure and microstructure between Cu-Sn 6% alloy produced by sand casting and by powder metallurgy. During sand casting process, the metal was melted in the furnace and then poured in to the sand mold, whilst in the powder metallurgy process; the metal powder was compacted in the metal mould and then heated to a temperature below its melting point (sintering process). In this research, the powder was compacted at 200 MPa and then sintered at 800° C for 45 minutes. The observation of the microstructure showed that the Cu-Sn 6%  alloy produced by powder metallurgy possessed more porositythan produced by sand casting. The sand casting process produced the Cu-Sn 6% alloy with Brinell Hardness Number (BHN) of 47.97 kgf/mm2 and compressive strength of 680.8 MPa. The powder metallurgy process produced the Cu-Sn 6% alloy with Brinell Hardness Number (BHN) of 27.08 kgf/mm2 and compressive strength of 944.4 MPa.
Strategi Penawaran dalam Industri Konstruksi (Studi Kasus di Layanan Pengadaan Secara Elektronik, Kota Bandung) Hakas Prayuda, Mandiyo Priyo ,
Jurnal Semesta Teknika Vol 16, No 1 (2013): MEI 2013
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The aims of this research are to calculate the value of mark-up using bidding strategy approach and to determine the best bidding strategy to win a tender with the optimum mark-up value and the optimum profit. The data being used in this research are auction data that have been completed in 2010-2012 at LPSE Bandung using statistical approach namely discrete multi distribution, normal multi distribution, and single normal distribution. Bidding strategy methods being used are Friedman Method, Gates Method, and Ackoff & Sasieni Method. The Friedman Method can generate an optimum mark-up of 10% with expected profit of -0.0014, an optimum mark-up of -9% with expected profit of -0.0003, and an optimum mark-up of -1%  with expected profit -0.0004 for discrete multi-distribution, multi-normal distribution, and  single normal distribution, respectively. The Gates Methods can produce an optimum mark up of 6% with expected profit of 1,5000, an optimum mark up of 5% with expected profit 0.0097, and an optimum mark up of 6% with expected profit 1.2888 for discrete multi distribution, multi-normal distribution, and single normal distribution, respectively. While the Ackoff & Sasieni Methods can generates an optimum mark-up of -2%  with expected profit -0.0003, an optimum mark-up of  1% with expected profit for 0,0013 for discrete multi distribution, and for both multi and single normal distributions, respectively.

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