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Ashadi Salim
Bina Nusantara University
Computer Science & IT Engineering Mathematics

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Journal : comtech computer mathematics and engineering applications

 1 
Integrating Preventive Maintenance Scheduling As Probability Machine Failure And Batch Production Scheduling Zahedi Zahedi; Ashadi Salim
ComTech: Computer, Mathematics and Engineering Applications Vol. 7 No. 2 (2016): ComTech
Publisher : Bina Nusantara University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21512/comtech.v7i2.2247

Abstract

This paper discusses integrated model of batch production scheduling and machine maintenance scheduling. Batch production scheduling uses minimize total actual flow time criteria and machine maintenance scheduling uses the probability of machine failure based on Weibull distribution. The model assumed no nonconforming parts in a planning horizon. The model shows an increase in the number of the batch (length of production run) up to a certain limit will minimize the total actual flow time. Meanwhile, an increase in the length of production run will implicate an increase in the number of PM. An example was given to show how the model and algorithm work.
Pengukuran Modulus Elastisitas Dinamis Batuan dengan Metode Seismik Refraksi Ashadi Salim
ComTech: Computer, Mathematics and Engineering Applications Vol. 3 No. 2 (2012): ComTech
Publisher : Bina Nusantara University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21512/comtech.v3i2.2331

Abstract

The seismic wave velocity in rock formation depends on the elastic modulus and mass density of rock where the wave travels. The velocity measurement of P and S waves on rock formation and the mass density in the laboratory can be used for calculating the elastic modulus of rock formation. The elastic modulus is part of rock mechanical parameter needed in geological engineering researches. The velocity measurement of P and S waves by the seismic refraction method was done on a tunnel with 11 spreads of measurement. From the results of the measurement, three groups of rock formation could be identified. The first is rock formation with Ed=8.890-12.68 MPa and G=3.306-4.830MPa; the second group is rock formation with Ed=8.890-12.68 MPa and G=3.306-4.830MPa; and the third group is with Ed=18.520-21.120MPa and G=6.724-7.744MP. The first group is clay formation while the second and third groups are andesitic stone formation. 
Analisis Data Seismik Refraksi dengan Metode Generalized-Reciprocal Ashadi Salim
ComTech: Computer, Mathematics and Engineering Applications Vol. 3 No. 1 (2012): ComTech
Publisher : Bina Nusantara University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21512/comtech.v3i1.2397

Abstract

The analysis of seismic refraction data by the generalized reciprocal method can be used for delineating undulating refractors. The forward and reverse times of arrival at different geophones with XY distance along a refraction profile, are used for calculating time depth. The seismic wave velocity in refractor may be obtained from velocity analysis function, and the depth of refractor under each geophone is obtained from time-depths function. This method has been applied at one line of seismic refraction measurement that was 440 m long with 45 geophone positions. The measurement obtained 20 m as the optimum XY-value and 2250 m/s as the velocity of seismic wave in refractor, and the undulating refractor topography with the depths varies 10.4 – 22.1 m. The optimum XY-value was obtained from approximate calculation derived from the observation, that was indicated the absent of undetected layer.
Pengukuran Panjang Simulasi Retak Permukaan dengan Teknik Perambatan Gelombang Ultrasonik Permukaan Ashadi Salim
ComTech: Computer, Mathematics and Engineering Applications Vol. 2 No. 1 (2011): ComTech
Publisher : Bina Nusantara University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21512/comtech.v2i1.2725

Abstract

The length measurement of the surface crack simulation using surface ultrasonic wave method is performed for surface crack length of 5, 10, 15, 17.5, 20 and 22.5 mm. Each crack has the orientation of 22.50, 450, 67.50, and 900 against the surface of the sample. The method is similar to the transmission technique, where the transmitting and receiving probes are arranged face-to-face against the crack mouth. The surface wave pulse is high enough to be distinguished from the pulse of the coming waves as the result of mode conversion that occurs from the crack tip. The deviation of the measurement of the length was 8% in the average. 
Co-Authors Zahedi .