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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 22 Documents
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Search results for , issue "Vol 12, No 1 (2009): MEI 2009" : 22 Documents clear
Analisis Rekayasa dan Karakterisasi Briket Bahan Bakar dari Limbah Serat Kenaf Sudarja, Sudarja
Jurnal Semesta Teknika Vol 12, No 1 (2009): MEI 2009
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The amount of rejected hibiscus cannabinus fiber reaches 30% during harvesting and 10% of the fiber bought by industries because they are not satisfied the quality requirement. In other words, 37% of the harvested hibiscus cannabinus fiber is rejected and become waste. On the other hand, the society need alternative fuel instead of fossil fuel due to its availability and high-price. Therefore, a study on the utilization of hibiscus cannabinus fiber waste for alternative fuel is urgently required. The main materials used in this research are hibiscus cannabinus fiber waste and starch glue. The first step is producing star-coal by burning the hibiscus cannabinus fiber in a closed tube (chamber) followed by producing starcoal briquette by blending starcoal powder and starch glue, and finally, pressing it in a pressing machine. The characteristic being studied are: water content (comply to ASTM-D-3173), calorific value (ASTM D-2015 and ASTM D-5865-03), and ash content (ASTM D-3174). The result of the research shows that the average calorific value of hibiscus cannabinus fiber waste is 6595,65 kal/gram while that of the briquette compacted  at 1090 psi or above was 7394,14 kal/gram. The average water content was 10,9%, and ash content is 31,67%. Advanced study concerning the percentage of fly ash and economic aspects was recommended in order to justify its feasibility.
Analisis Kinerja dan Tarif Angkutan Umum Bus Jurusan Surakarta-Yogyakarta: Studi Kasus pada Bus Langsung Jaya, Jaya Putra dan Sri Mulyo Suwardi, Suwardi
Jurnal Semesta Teknika Vol 12, No 1 (2009): MEI 2009
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One of the supporting factors to improve connection between Surakarta and Yogyakarta, is the adequacy of public transportation. With the existence of adequate public transportation that meet the standard, especially Yogyakarta – Surakarta buses, activities in the two cities can be expected to increase. The activities can be economic, politic, social, safety, scientific or the others.  The existing public transportation between Surakarta – Yogyakarta, needs to be evaluated because public might not satisfy the standard. The objective of the research is to analyse the operational cost and tariff of public buses serving Yogyakarta – Surakarta line.  The method of this research is descriptive analysis.  In this research, public work on transportation in this region was analyzed in order to improve its condition in the future. Primary data include the number of passenger, travel time, departure and arrival time.  Secondary data obtained from the bus companies consist of direct and indirect operational costs, as well as fixed and variable cost. The results show that the passenger tariff after yield analysis with headway 4 minutes and the average load factor of 55.83% is IDR 8,720. At headway of  4 minutes and passenger tariff of IDR 8,000 bus companies are still suffering from loss. If the headway changed to 6 minutes , the load factor became  83.75%  and the passenger tariff of IDR 5,800. It is lower than the current passenger tariff of IDR 8,000. The changing of headway from 4 minutes to 6 minutes may increase bus company profit by 27%. 
Sekam Padi Untuk Proses Pack Karburising Baja Karbon Rendah Soemowidagdo, Arianto Leman
Jurnal Semesta Teknika Vol 12, No 1 (2009): MEI 2009
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The effectiveness of rice husk on pack carburizing process of low-carbon steel was investigated. The process was carried out at 850°C for 2, 4 and 6 hours. Carbon content of the specimen materials is 0.082%. Rice husk charcoal and rice husk powder was then compared to graphite powder. All of the media were sifted on 50 mesh sieve. After the process, all specimens were reheated up to 850°C, and then, hold it for 5 minutes. Subsequently, they were quenched into water at 28°C. The result shows that the effectiveness of rice husk charcoal is better than those of other media being used in the investigation. Six hours pack carburizing utilized, rice husk charcoal resulted in the enhancement of steel surface hardness from 122 VHN to 465 VHN and increase of the proportion of martensite structure.
Analisis Arus Jenuh dan Panjang Antrian pada Simpang Bersinyal: Studi Kasus di Jalan Dr. Sutomo-Suryopranoto, Yogyakarta Rahayu, Gati; Rosyidi, Sri Atmaja P; Munawar, Ahmad
Jurnal Semesta Teknika Vol 12, No 1 (2009): MEI 2009
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The aim of this paper is to analyse the delay length based on MKJI (1997). A case study was conducted on a signalized junction of Dr.Sutomo-Suryopranoto road, Yogyakarta. The correction was carried out on coefficient of basic saturation flow in ranging from 600 to 2200. Therefore, the predicted (from MKJI 1997) and measured delay length was compared. The results show that the coefficient on basic saturation flow calculation needs to be modified in the range of 600 to 2200 in order to find the similar length of the delay between prediction and field measurement. Passenger car unit (PCU) unit for motorcycle from MKJI (1997) was also corrected from 0.2 to 0.15. 
Pengaruh Faktor Lingkungan terhadap Strategi dan Kinerja Industri Manufaktur di Jawa Timur Hidayat, Rachmad; Budiarto, Hairil
Jurnal Semesta Teknika Vol 12, No 1 (2009): MEI 2009
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This research examined the influence of environment factors (industrial, operational and remote) on the strategy and performance of manufacturing industries in East Java. The Structural Equation Modeling (SEM) was employed to test the hypotheses which emerged from the observed conditions. Moreover, the AMOS 4.0 was also used to perform the SEM. The results showed that the environment factors, i.e. industrial and operational environments as well as remote environments jointly affect the understanding of the environment industry matching with industry and environmental operational environment to establish its strategic objectives as an effort to achieve optimum performance manufacturing industries in East Java. Industrial environment conditions cannot be isolated from the global crisis because most industries prefer to concentric diversification strategy where new product technologies have a relevance to existing products.
Experimental Investigation of Seismic Parameters and Bearing Capacity of Pavement Subgrade Using Surface Wave Method Widodo, Wahyu
Jurnal Semesta Teknika Vol 12, No 1 (2009): MEI 2009
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The spectral analysis of surface waves (SASW) method is introduced as an in-situ non-destructive seismic technique where the method consists of the generation, measurement and processing the dispersive Rayleigh waves from two vertical transducers. Subsequently, the dispersive data of Rayleigh phase velocity are inverted and the shear wave velocity versus depth of the site is obtained. The dynamic stiffness parameters, i.e. elastic modulus generated from the SASW measurements are at a very small strain levels of < 0.001%. At this strain level the soil is linearly elastic and the use of elastic theories is thus justified. The aim of this paper is to investigate the seismic parameters of the pavement subgrade stiffness using the SASW method and to predict its bearing capacity based on the seismic parameters. In order to determine the bearing capacity, in situ dynamic cone penetrometer (DCP) was also carried out in the same location of SASW test.  The relationship of the shear wave velocity and dynamic elastic modulus (Edynamic) of the SASW were found to be in good correlation with bearing capacity obtained by the DCP. 
Peningkatan Nilai CBR Laboratorium Rendaman Tanah dengan Campuran Kapur, Abu Sekam Padi dan Serat Karung Plastik Widianti, Anita
Jurnal Semesta Teknika Vol 12, No 1 (2009): MEI 2009
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Bearing capacity of a subgrade is one of the parameters to design the thickness of road pavement. Beside the bearing capacity, swelling behavior of subgrade must be in a narrow range to avoid crack of the pavement. This paper presents an effort to improve the soaked design California Bearing Ratio (CBR) and swelling value of soil by stabilizing with lime-rice husk ash and strengthened by randomly placed plastic fiber. In this study, the portions of lime and rice husk ash were set constant to the value of 12% and 24%, respectively. Amount of waste plastic sack fibers was used in this experiment ranging from 0.1% to 1.2% of dry weight of mixtures. The samples were tested at 7 and 14 days after mixing. The results show that the soaked design CBR value increases to 867%. As a result, swelling value decreases from 62% to 100%. The optimal improvement of the soaked design CBR was found at 0.2% of plastic sack fibers.
Analisis Kinerja Kontraktor yang Menerapkan Sistem Manajemen Mutu ISO-9000 Priyo, Mandiyo
Jurnal Semesta Teknika Vol 12, No 1 (2009): MEI 2009
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The growth in the implementation of quality management system standard as an instrument to win global market competition and to improve product and service quality has affected not only manufacturing industries but also construction industries. One of the standards that is most widely implemented by companies or organizations in quality management system may be the ISO 9000. It should be noted that the ISO 9000 is not a standard for products or services, but it is a standard for quality management system employed in their production process. The objective of this research is to study the implementation of the ISO 9000 standard by the PT. Wijaya Karya Beton that has adopted the ISO 9000 for its quality management system standard. In addition, the criteria for evaluating its performance have also been identified. This criterion includes written procedure and its consistent implementation, as well as the measurement of the implementation result of its operation process flow and working procedures. This research was carried out by means of performance measurement, i.e. qualitatively by employing questionnaire, scoring and measurement on productivity and targeted quality achievement such as rework rate and reject rate. The data were collected by observation, extraction from the internal and external quality audit report, as well as daily-, weekly- and monthly reports on the pile production. The effect of company’s performance that employs the ISO 9000 standard (qualitative measurement) on the productivity, rework rate and reject rate (quantitative measurement) were analysed using Pearson’s Product Moment correlation analysis technique. The result reveals that the qualitative measurement resulted in continuous performance improvement, so did the quantitative measurement. It showed that these two measurement methods tends to be in a good agreement. A general conclusion that can be drawn is that the ISO 9000 has been properly implemented in the PT. Wijaya Karya Beton.
Pengaruh Lapisan Pasir di Bawah Fondasi terhadap Redaman dan Frekuensi Natural Akibat Beban Gempa Pujianto, As’at
Jurnal Semesta Teknika Vol 12, No 1 (2009): MEI 2009
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Sand layer under foundation has been widely used for vibration damping by an earthquake since centuries ago. Due to being located in earthquake-zone and sand as natural material is widely distributed over regions, research on the use of sand for earthquake vibration damping is becoming important in Indonesia. The aim of this work is to study sand layer behavior in reducing earthquake vibration. Parameters of soil structure, i.e. damping ratio, displacement, soil pressure, and the change of natural frequencydue to the existence of sand layer under foundation were observed. In this study, soil structure was modeled as layered soil profile where top layer is a clay soil layer. Foundation base is located at a depth of 300 cm underlying varied thicknesses of course sand layer, i.e. 0, 50, 100, 150 and 200 cm under foundation. In order to produce various soil pressures, load magnitudes of 0, 10,000, 20,000, 30,000 and 40,000 tons were selected. Therefore, earthquake loadings with high and low frequency from Koyna and Bucharest earthquake record were implemented to soil structure models. Results showed that the increase of sand layer thickness does not essentially affect to the decrease of displacement. It is depending on the frequency of an earthquake. However, a thickness of 50 cm shows decrease of displacement due to high and low frequency earthwuake loading with the average deviation of 3.67 %. The displacement due to Bucharest earthquake loading is greater than that of Koyna earthquake, with the average ratio of 9.38 times. If ground frequency is higher than earthquake frequency, ground displacement is becoming smaller.
Penggunaan Campuran Abu Sampah Organik dan Limbah Karbit sebagai Bahan Pengganti Semen pada Mortar Hartono, Edi; ZA, Siti Rofi’ah; Hemeto, Abd Dzargifar
Jurnal Semesta Teknika Vol 12, No 1 (2009): MEI 2009
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Organic waste and calcium carbide waste can be used as replacement material for cement in mortar. Organic waste ash and calcium carbide waste are mixed with some variations and then conducted tests to obtain the characteristics of the materials used in this study. Content of mortar comparation base on weight that are organic waste-calcium carbide waste : sand : water of 1.0 : 2.75 : 1.0. Compositions of waste organic ash and calcium carbide waste have some variations, i.e., 0.9-0.1, 0.7-0.3, 0.5-0.5, 0.3-0.7 and 0.1-0.9. Control mortar also made as discussant for mixture variations of organic waste ash and calcium carbide waste in compressive strength test. Control is mortar mixed with common Portland cement. All of mortars are mold with molder that has dimension 5 cm × 5 cm × 5 cm. Compressive strength test is done when age of mortars is 3 days, 14 days, and 28 days. Based on laboratory test results, compressive strength on 14 days at the highest variation of 70 % organic waste ash and 30 % calcium carbide waste was found to be 26,7 kg/cm2. But, this result of compressive strength is lower compared to compressive strength of control mortar which was found to be 79.9 kg/cm2 on 14 days. Highest compressive strength of all mixture variation showed that mixture of waste organic ash and calcium carbide waste can be used as a mortar/mixture of brick pair in simple house type and very simple house type that needs compressive strength as much as 25 kg/cm2for wall that do not bear of load. 

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