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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 20 Documents
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Search results for , issue "Vol 18, No 1 (2015): MEI 2015" : 20 Documents clear
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.
Implementasi Arsitektur Operational Data Store (ODS) dan Dimensional Data Store (DDS) dalam Pembangunan Data Mart Lulusan Bakhtiar, Rohmana Zulfa; Riyadi, Slamet; Asroni, Asroni
Semesta Teknika Vol 18, No 1 (2015): MEI 2015
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Universitas Muhammadiyah Yogyakarta (UMY) is a big and high-grade educational institution. During the period of 1998-2014, UMY has produced about 20550 graduates. But, the big number of graduates is not supported by a good data storage system. Whereas those data are needed in filling up the accreditation form. For that reason, we have to build an integrated data storage system to provide graduates data as needed, that is graduate data mart. The development of graduate data mart uses SDLC Model Waterfall method. This method involves several types, there are requirement analysis, design system, implementation system, testing system, and maintenance system and those must be done sequentially. If there is an error, the process must be repeated from the beginning to fix the error. Development of graduate data mart uses Operational Data Store (ODS) and Dimensional Data Store (DDS) architecture. Those architectures are selected because they support transactional level. By using those architectures, graduate data mart is capable to display the data of graduates on the academic year, GPA, educational years, and the status of the student transfers. As the result, those data are able to help the management of university in filling up the accreditation form.
Analisis Cacat Las Incomplete Fusion Dan Retak Memanjang Pada Waterwall Tube Boiler PLTU Paiton Unit 1 Sahlan, Sahlan
Semesta Teknika Vol 18, No 1 (2015): MEI 2015
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Weld defects in the form of "incomplete fusion" and lengthwise (longitudinal) crackswas observed at the boiler tube welding of steam power plants of Paiton Unit 1, row 3, located860 mm above theheader, .Incomplete fusionmay be caused by incorrect use of the the magnitude of current,welding speed, or manipulation or selection of the electrode being used, thatmay lead tounevenfusityand affect generate the cracks along the incomplete fusion region. Incomplete fusion defects in the waterwall tubes welding being visible from the edge of the boundary between the base material and weld region with the presence of indentation or depression in the form of a very deep crater welding. Indentations or hollows, that will be observed more clearly by using an optical microscope with a magnification 1000X, which in the presence of imperfections observed molecular fusion between grain boundaries and inter-molecular crystal. At 1000X magnification ofthe HAZ (heat affected zone) region,transition structure forming brittle fractures was observed 
Karakteristik Kecelakaan Lalu Lintas dan Pendidikan Keselamatan Berlalulintas Sejak Usia Dini: Studi Kasus di Kabupaten Purbalingga Sugiyanto, Gito; Santi, Mina Yumei
Semesta Teknika Vol 18, No 1 (2015): MEI 2015
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Traffic accidents increased along with the increase in road traffic violations. One of the victims of traffic accidents is children. Road safety awareness and culture of children can be improved by doing the traffic safety education from an early age and promotion of the importance of road safety for children. Pedestrian is one of the vulnerable road users. The aim of this study is to investigate the characteristics of traffic accident in Purbalingga District, Central Java Province and the characteristics of the vehicle speed on arterial roads without median and introduces the principle of crossing the road by using 4-T procedure that is (Tunggu sejenak, Tengok kanan, Tengok kiri, dan Tengok kanan lagi) or waiting for a moment, look right, look left, and look right again to children from an early age. Based on the analysisof an accident data from 2010 till 2013, motorcycles are vehicles most involved accident followed by truck.Characteristics of speed in arterial roads without median with the function as a school district obtained a mean of the speed is 56.80 km/h. The probability of a pedestrian who was hit motorcycle or car passengers with this speed (56.80 km/h) will die is 90%.
Analisis Unjuk Kerja Boiler Feed Pump Turbine Untuk Kapasitas Ketel Uap 2000 Ton/Jam Di PLTU Cirebon Jawa Barat Sukamta, Sukamta; Sudarja, Sudarja; Wathon, Muhammad Mujaddid Ighna
Semesta Teknika Vol 18, No 1 (2015): MEI 2015
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Boiler feed pump turbine (BFPT) has an important role in the circulating of demin water from deaerator to the separator of  steam power plant operations (PLTU) in Cirebon. Flow rate, temperature and  pressure were important parameters in boiler feed pump process. Based on the BFPT function, it was necessary to do the analysis interpretation of the performance BFPT. Data needed for evaluation include pressure and temperature on the suction, pressure and temperature on the discharge, and flow capacity. In this study, the data were taken starting in January to December 2014. Data processing was performed using a centrifugal pump calculations, presented in tables and graphs using MS Excel. Analysis of data using qualitative interpretation of quantitative data. BFPT efficiency during operations in 2014 decreased in February - March amounted to 17.91% (BFPT A) and 18.04% (BFPT B). BFPT A highest efficiency obtained in January amounted to 73.76%, the lowest in March amounted to 55.45%. The highest efficiency BFPT B in February amounted to 72.94%, the lowest in March amounted to 54.9%. Change of Performance BFPT occur due to changes load generator power plant that led to the pressure change  and flow capacity. Other factors that degrade the performance because BFPT was operated continuously for 24 hours and the age of  BFPT sufficient old  cause decrease in pump performance.
Penerapan Metode K-Means Untuk Clustering Mahasiswa Berdasarkan Nilai Akademik Dengan Weka Interface Studi Kasus Pada Jurusan Teknik Informatika UMM Magelang Asroni, Asroni; Adrian, Ronald
Semesta Teknika Vol 18, No 1 (2015): MEI 2015
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The selection process among outstanding students in a department has a big problem. This process is not fair because only involve one criteria and ignore the other criteria. We need the best student to participate in a competition held by the Indonesia Security Incident Response Team on Internet Infrastructure (ID SIRTII) of the Ministry of Communication and Information. This process uses Weka software to calculate the best student. It provides the various method to explore the data. One of them is clustering method. There are many algorithms in clustering method. In this research, we will investigate widely about one of that algorithms. Its name is K-Means. This algorithm (K-Means) will give the recommendations about the best student based on the cluster. It will represent the many clusters of a student group. The best cluster can be calculated more to get the names of the best students group. They are eligible to enter the competition.  K-means involve the GPA (Grade Point Average) and related course to support the academic skill in order to get the best student. This research helps the teacher select the best student to enter the competition. Many similar cases can use this algorithm in order to get the best student.
Aplikasi Metode Time Cost Trade Off Pada Proyek Konstruksi: Studi Kasus Proyek Pembangunan Gedung Indonesia Priyo, Mandiyo; Aulia, Muhamad Raa’uf
Semesta Teknika Vol 18, No 1 (2015): MEI 2015
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Time and cost are very infuential to the success and failure of a project. The measurement of project can be seen by the short time arrangment and minimum cost without denying the quality of project result. Systematically project management is very needed to make sure the time of project realization appropriate with the contract or it can be done faster so the cost will be able to be pressed. Moreover it is also to avoid paying the fine caused by the project lateness. The purpose of this research is to calculate the cost change and time project arrangment by adding work time variation and employed increment, then compare the result between fine cost and cost changing after the overtime and employee increment. Data in this research is secondary data from implementer contractor. Data analysis is used Microsoft Project 2007 program and time cost trade off method. The result from Microsoft Project 2007 program is critical path and result from time cost trade off method is duration velocity and increment cost in every activity that fasten. The result of this research indicated that (1) Time and cost optimum result of the adding work time (overtime) obtained at the age of project 242 days of work with total cost of project Rp. 10.481.732.644,58 with time efficiency project 24 days (9,02%) and cost efficiency project Rp. 43.019.556,39 (0,41%). (2) Time and cost optimum result of the employee increment obtained at the age of project 243 days of work with total cost project  Rp. 10.482.934.084,43 with time efficiency project 23 days (8,65%) and cost efficiency project Rp. 41.818.116,54 (0,40%). (3) The best choise is with adding work time (overtime), because it produces time and cost efficiency highest with time efficiency project 24 days (9,02%) and cost efficiency project Rp. 43.019.556,39 (0,41%). (4) Cost expedite duration project (adding overtime or employee increment) cheaper than the cost that should be paid if the project failed and have to pay the fine.
Penyiraman Otomatis Pada Tanaman Atap Rumput Gajah Al-Muqorrobin, Muhammad Izzuddin; Chamim, Anna Nur Nazzilah
Semesta Teknika Vol 18, No 1 (2015): MEI 2015
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Watering is an important step to mantain the condition of a plant, but most people dont know how good watering is, like the time of watering, watering composition that match with the plant. Almost all of green roof in any type is not using automatic system but manually watering it, that make watering the green roof become very hard to do. In this case, many people think that having a green roof is very difficult, especially in maintain it. From this problem, writer want to convince people that having a green roof is not as difficult as it look. With combining the watering methode, green roof, and surface irrigation, then writer want to make something that can help people to mantain plant especially green roof plant. The objective of this papers is to make and to know how Green Roof Automatic Watering System’s work. Using Atmega16 chip, writer made an electronic circuit that programmed by C language that will automatically watering the plant if the sensor detect the percantage above 10%. The sensor is a couple of bar that transmit voltage in between the bar past through the soil. The sensor then will transmit the data to Chip to be processed, and if they meet the condition, the IC MOC3021 will be activated, then the AC Current will automatically charge the load (pump). This electronic circuit then applied to a prototype of extensive green roof with 30’ which is a diagonal. Layering of the green roof from the first to the last is waterproof, cubical fern root (to maintain water cyclus), soil, and the plant (especially grass type). From the application, writer can make a conclusion that this green roof automatic watering system work well and can stand up to 1 month use.
Dampak Parkir Khusus Wisata Terhadap Simpang Bersinyal Jalan Perkotaan: Studi Kasus Persimpangan Ngabean, Yogyakarta Mahmudah, Noor; Tubagus, Adhytia
Semesta Teknika Vol 18, No 1 (2015): MEI 2015
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The development of Special Region of Yogyakarta has been occuring rapidly due to this region is well known as student city and the primary tourism destination in Indonesia. One of the transportation problems related to the tourism activities is traffic conflict due to parking area of tourism bus in Ngabean, Yogyakarta City. Therefore it is needed to evaluate signalized junction around the parking area in order to reach the optimal performance. The study carried out among other by conducting field survey to the existing condition (performance) of signalized junction either in the weekend (Saturday) and weekday (Monday), especially by evaluating the degree of saturation (ds). The analysis results showed that the degree of saturation in the weekend is 0,89, which is higher than the allowed one (ds=0,85). Since the degree of saturation in the weekday is 0,76 so it is relatively good. The scenarios (model) applied to improve the overall junction performance are by estricting (prohibiting) left turning on red (LTOR) and by carrying out road widening. The final result obtained from the scenario (model) is the degree of saturation (ds) becomes lower than the allowed value (0,83<0,85) for all approaches in the signalized junction. 
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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