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| Articles
by
Wirawan |
Total Records (
3 ) for
Wirawan |
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Endang Widjiati
,
Eko Budi Djatmiko
,
Wisnu Wardhana
and
Wirawan
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Analysing characteristics of propeller cavitation noise is necessary in relation with the identification of noise signature in conjunction with both surface ship and submarine operations. Since, the noise signature is determined by propeller, flow and machinery noise then any vessel that has certain propeller, hull shape and machines will have a peculiar signature. The propeller cavitation noise can be generated by means of experiment performed in a cavitation tunnel. This study reports some results of the noise characterization experiment conducted in the Cavitation Tunnel available at the Indonesian Hydrodynamic Laboratory, Surabaya, Indonesia. Two B-series propeller models, i.e., 4 and 7-blade were studied in the experiment. Time-Frequency distribution, namely Wigner-Ville Distribution (WVD) is applied to observe the characteristics of the cavitation noise. Results show that the WVD can differentiate whether the propeller cavitation noise is generated either by the 4 or 7-blade propeller. In this study, three different kinds of categories in the appearance of cavitation are distinguished, i.e., when the propeller does not experience cavitation, if only hub and tip vortex cavitation develop and when various cavitations occur simultaneously. |
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Tri Budi Santoso
,
Endang Widjiati
,
Wirawan
and
Gamantyo Hendrantoro
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Understanding of channel propagation characteristics is a key to the optimal design of underwater
acoustic communication. Generally, modelling of underwater acoustic channel is performed based on
measurement result in certain site at certain times. Different sites might have different characteristics each of
which can generally be described by a model obtained by averaging measurement results at multiple points in
the same environment. This study describes a characterization of the underwater acoustic channel of tropical
shallow water in a Mangrove estuary which has sediment up to 60 cm at the bottom. Such a channel model is
beneficial for the design of communication system in an autonomous underwater vehicle for instance. The
measurement result of delay spread parameter from three different points with the distance of 14~52 m has
various values. The Root Mean Square (RMS) of delay spread ranges between 0.0621~0.264 msec and the
maximum delay spread varies with the value of 0.187~1.0 msec. The PDF fitting shows that Rayleigh distribution
describes the fading variation more accurately than Nakagami and Ricean. |
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Syamsul Hadi
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Anggit. Murdani
,
Wirawan
,
Haris Puspito Buwono
and
Imam Muda Nauri
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Changes in tensile strength of recycled
aluminium from the piston as a problem encountered. The
objective of this research is to know the tensile strength of
recycled aluminium from piston for the next use. The
methods used are: design and manufacture of tensile
specimen mold, specimen casting, tensile testing, material
composition testing and data analysis. The test results
showed that the tensile strength of the motorcycle piston
aluminium worth 376 MPa was decreased to 191 MPa for
the 1st recycled (49%) from the 1st recycled to the 2nd
recycled value of 118 MPa (38.3%) and from 2nd recycled
to 3rd recycled worth 117 MPa (0.8%) caused by loss of
elements during recycling include Cu, Si and Fe. The
shrinkage tolerance in a successful foundry into a tensile
test specimen is smaller than 6%. The SEM photographs
show that the porosity of the 3rd recycled aluminium is
less than in the 2nd and 1st recycled which means the
solubility of the alloying element is preferable, wherein
the insoluble elements (Cu, Si and Fe) are decreased. |
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