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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 19 Documents
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Search results for , issue "Vol 11, No 1 (2008): MEI 2008" : 19 Documents clear
Pemilihan Mesin Welding Otomatis Dengan Penerapan Value Engineering Dan Analitical Hierarchy Process Andesta, Deny; Nuruddin, Moch
Jurnal Semesta Teknika Vol 11, No 1 (2008): MEI 2008
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Abstract

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.
Pengaruh Waktu Pengeringan Dan Tempering Terhadap Mutu Beras Pada Pengeringan Gabah Lapisan Tipis Prasetyo, Totok; A, Kamaruddin; D, Made K; T, Armansyah H; N, Leopold
Jurnal Semesta Teknika Vol 11, No 1 (2008): MEI 2008
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The aim of this research was to determine the effect of various drying and tempering durations on rice quality using thin layer drying. The drying procedure consist four satge; first rough rice was dried in a drying chamber for various durations to remove 5 to 8 % moisture content (M.C). In the second stage rice was tempered under the room temperature for certain duration, to reduce MC gradients within the kernels. tempering period. The rice was then dried further to reach the final 14 % M.C. After the second drying the rice was tempered. Drying process was conducted using  heated air at temperature of either 50 0C, RH 26%  or  60 0C, RH 17%. The results  show that very small  reduction in Head Rice Yield (HRY) when  less than 6 % m.c, were removed during the first drying stage. Effects on HRY was obeserved when the moisture removal was greater than 6% m.c. during the 1st drying stage. It was also observed that tempering time could not prevent the reduction in HRY when moisture remomal was higher than 6% M.C. during the 1st drying stage.
Peningkatan Citra Untuk Memperjelas Foto Brain Ct Scan Yulianto, Priyono
Jurnal Semesta Teknika Vol 11, No 1 (2008): MEI 2008
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The CT scan brain photo represent medical image result from Computer Tomographi (CT) Scanner process, normally obtained on photographic negative transparencies. The brain images were acquired from a CT scan photo presenting colour gradation in to gray level, that is : white colour, gray and black colour. In general have histogram which tend to reside in around dark in to gray level, so that its image less clear if seen with naked eye. and can be told exploiting of digital image enhancement not yet is optimal. The research was to show that digital image enhancement used to clarify photograph CT scan brain image. Data collecting done with procedure chosen normal diagnostic CT-scan brain photo and which have indication damage of brain effect of ischemic stroke. The CT scan brain photo so that can be processed must be done scanning beforehand for the image digitization is quantization. The image enhancement techniques can be processed is : histogram equalization transform, contrast stretching transform, histogram classify, region of interst to enhancement and edge detection. Histogram equalization (Histeq) transform, contrast stretching transform, histogram classify, region of interst to enhancement (ROI) and edge detection transform can be used for clarify CT scan brain photo, so that can assist radiology doctor in is diagnostic of disparity or damage brain effect of ischemic stroke. 
Model Cabut-Serat Nylon 600 Tertanam Dalam Matriks Sementitis Berbasis Fraktur Susilorini, Retno
Jurnal Semesta Teknika Vol 11, No 1 (2008): MEI 2008
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The fracture mechanics is known as a fracture based approach to prohibit a catastrophic failure of structure. In micro scale field, the fracture mechanics is implemented especially to determine the performance of interface between fiber and cementitious matrix in ‘fiber-reinforced cementitious composite’. The studies and applications of nylon clearly define the advance characteristic of nylon may influence the overall performance of composites and become a crucial issue to be learned, therefore, this paper forwards a fractured based pull-out model of short nylon 600 embedded in cementitious matrix with main concern on fracture phenomenon. The research applies experiment that applies pull-out test with embedded nylon 600 in cementitious matrixand the analytical method that constructs the fractured based pull-out model. The experiment results show the specimens with pull-out fibers have embedded length lf = 30-60 mm and the broken fibers lf = 70-100 mm. The pull-out test also shows several stages: (a) Pre-slip stage, (b) Slip stage, and (c) Strain-hardening stage. The model fits to experimental results. Several theories meet conclusions: (a) Whenever fracture takes place, it is always an unstable crack, (b) Stable cracks are established by the presence of crack arrester, (c) There is no way directly to determine the length of stable crack, but it still can be determined by fractured based approach, (d) The length of stable crack is determined by the position of crack arrester, (e) There is an equation derived for pull-out model (f) There is an equation to determine the stable crack length, (g) Stable cracks may be used to determined the bond capacity, (h) After the establishment of stable cracks, increasing strain beyond  strain e1 will not increase stress s1, hence do not induce additional fracture, (i) Increasing of strain e after the establishment of stable cracks will increase stress s, then the second slip will not take place, (j) Broken nylon fibers have a longer embedded length because of the possibility of crack arrester presence is bigger than the shorter ones.
Pengaruh Perlakuan Panas Terhadap Struktur Mikro Logam St 60 Yani, Rina Dwi; Pratomo, Tri; Cahyono, Hendro
Jurnal Semesta Teknika Vol 11, No 1 (2008): MEI 2008
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This research aim to know the transformation of microstructure and it influence to ST 60 when its heated by heat treatment process. Specimen heated and arrested at temperature 800°C during 30 minutes, then is cooled with water coolant. Hardness of test piece is measured [by] before and after heat treatment by using method Rockwell C. Microstructure of metal photograph take by using special camera, and it presenting in millimeter block to calculate ferrite and pearlite content percentage. Result of research indicates that heat treatment to metal ST 60 causing microstructure change and percentage of ferrite was increase, directly causes material hardness value  increase too.
Mesin Pemisah Dan Pembersih Biji-Bijian / Butiran Sebagai Bahan Baku Pakan Burung Olahan Rofarsyam, Rofarsyam
Jurnal Semesta Teknika Vol 11, No 1 (2008): MEI 2008
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Bird feed  ingredient process has been done traditionally which uses winnow that moved up and down by hands, just reach 6 kg/hour by a worker, that containt of 5.75 kg of solid grains, 0.25 kg empety grains and dust. For rising work efficiency needs separating process and cleaning process bird feed ingredient between solid grains and empety grains and dust by mechanical. Those are by build bird feed ingredient separating and cleaning machine. Construction and working principle designed, according to theory of subtance free fall, which forced by horizontal windy force by blower and motored by electrical motor  ½ Hp 1450 rpm completed by belt and pulley transmition. Capacity of bird feed ingredient separating and cleaning machine can reach 90 kg/hour consist 86.25 kg solid grains and 3.75 kg empety grains and dust. 
Pengaruh Lokasi Ketebalan Maksimum Airfoil Simetris Terhadap Koefisien Angkat Aerodinamisnya Nurcahyadi, Teddy; Sudarja, Sudarja
Jurnal Semesta Teknika Vol 11, No 1 (2008): MEI 2008
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Airfoil performance data is regarded as highly valuable data in its wide area of application since it will help the designer, for examples; to predict the influence of rear spoiler mounting to the maneuverability and top speed of racing car, the thrust and fuel consumption needed for an aircraft to take off and cruise, or the power delivered by a wind turbine rotor at certain wind speed. The performance of airfoil, which is measured with its lift and drag coefficient, is greatly affected by its geometry and operating condition. The influence of various geometric and operational parameters to the airfoil performance is needed to be studied experimentally and the airfoil performance data obtained can be added to enrich the airfoil performance data base. The experiment was done by testing airfoil models by lift force direct measurements in a sub-sonic wind tunnel.  The type of airfoil used in this experiment is the symmetric airfoil with maximum thickness location as the geometric parameter and angle of attack with wind speed as the operational parameter being investigated for their influence to the lift and drag coefficient. The maximum thickness location was varied in 30%, 40%, and 50% of chord length measured from leading edge. The angle of attack was varied from 0o to 20o with 4o increments. The wind speed was varied from 10 m/s to 20 m/s with 2 m/s increments.  Parameters being measured were the free stream velocity, and the lift force. The result of the research shows that the best airfoil performance with lift coefficient 3,16 is achieved by the airfoil that has maximum thickness location in 40% of its chord length measured from its leading edge and operates at 20o angle of attack and 8,9  m/s free stream velocity.
Pengaruh Perubahan Kecepatan Pemakanan Terhadap Kekasaran Permukaan Pada Proses Pembubutan Hadimi, Hadimi
Jurnal Semesta Teknika Vol 11, No 1 (2008): MEI 2008
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 This research done to know existence of transformation influence of feeding speed at turning process to surface roughness of work substance. Specimen material is ST 37 with Ø 30, 40, 50 and 70 mm, with transformation of feeding speed 0,05, 0,069, 0,088, 0,125 and 0,17(mm/rev), depth of feed 0,2 mm, and speed of revolution of engine 950 rpm. Then the several assaying of surface roughness level of the specimen and calculation statistic by using one way variant analytical method based on data result of assaying. Result of research indicates that existence of influence significant to surface roughness value caused by transformation of feeding speed at specimen turning process Ø 30, 40, 50 and 70 mm, ST 37 material with depth of feed 0,25 mm and revolution of engine 950 rpm. Average of smallest roughness value is at Ø 30 mm yielding best surface roughness. This thing indicates that feeding speed and substance diameter lathed influential to surface roughness value.
Pengaruh Penambahan Limbah Peternakan Pada Karakteristik Pembakaran Batubara Wahyudi, Wahyudi; Santosa, Tito Haji Agung
Jurnal Semesta Teknika Vol 11, No 1 (2008): MEI 2008
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Using coal as a fuel is often obstacled  in harding of ignition. Waste of farming which is seldom used as  fuel possible to mix with coal. Research on solid fuel characteristic of combustion of  mixture between coal and waste of farming has been conducted to know the effect of mixture composisition toward rate of combustion. Experiment was conducted in a cylindrical combustion chamber which was heated and flowed with hot air. The content of volatile matter is higher in farming waste than in coal. In combustion of fuel mixture with higher content of farming waste, decreasing of mass of fuel mixture will more rapidly. The maximum combustion rate will higher in fuel mixture consisting more the waste of farming. 
Kompresi Citra Medis Menggunakan Alihragam Kosinus Diskret Dan Sistem Logika Fuzzy Adaptif Soesanti, Indah
Jurnal Semesta Teknika Vol 11, No 1 (2008): MEI 2008
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The required of bandwidth for communication of digital image data is increased. Limited channel capacity favors image compression techniques. These techniques attempt to minimize the number of bits needed to represent an image and to reconstruct it with little visible distortion. The image data compression techniques reduce memory of storage data and time needed to transmit data. One of the image data compression methods is using Discrete Cosine Transform and Adaptive Fuzzy Logic. The objective of this research is compressing medical image using Discrete Cosine Transform and Adaptive Fuzzy Logic System. Discrete Cosine Transform is applied to find the data will which be encoded and Adaptive Fuzzy Logic System is applied to classify sub image into certain class. The class classification of a sub image is according to their AC energy levels. The systems assign more bits to a sub image if the sub image contains much detail (large AC energy) and less bits if contains less detail (small AC energy). The result of the research shows that the accurate calculation of AC energy determines class classification of sub image and bitmaps used for image data compression must be matching with characteristic of image. Bitmaps used for image data compression determine compression ratio and reconstructed image quality. The medical image compression with ratio of 1:4.8028 result in a reconstruction image with SNR of 63.8197 dB, and visually shows that the image is similar to the original image without significant error.

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