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Journal of Engineering and Technological Sciences
Published by Institut Teknologi Bandung
ISSN : 23375779     EISSN : 23385502     DOI : -
Core Subject : Engineering,
Engineering
Journal of Engineering and Technological Sciences welcomes full research articles in the area of Engineering Sciences from the following subject areas: Aerospace Engineering, Biotechnology, Chemical Engineering, Civil Engineering, Electrical Engineering, Engineering Physics, Environmental Engineering, Industrial Engineering, Information Engineering, Mechanical Engineering, Material Science and Engineering, Manufacturing Processes, Microelectronics, Mining Engineering, Petroleum Engineering, and other application of physical, biological, chemical and mathematical sciences in engineering. Authors are invited to submit articles that have not been published previously and are not under consideration elsewhere. Starting from Vol. 35, No. 1, 2003, full articles published are available online at http://journal.itb.ac.id, and indexed by Scopus, Index Copernicus, Google Scholar, DOAJ, GetCITED, NewJour, Open J-Gate, The Elektronische Zeitschriftenbibliothek EZB by University Library of Regensburg, EBSCO Open Science Directory, Ei Compendex, Chemical Abstract Service (CAS) and Zurich Open Repository and Archive Journal Database. Publication History Formerly known as: ITB Journal of Engineering Science (2007 – 2012) Proceedings ITB on Engineering Science (2003 - 2007) Proceedings ITB (1961 - 2002)
Arjuna Subject : -
Articles 4 Documents
 1 
Search results for , issue "Vol. 40 No. 2 (2008)" : 4 Documents clear
An LPC Excitation Model using Wavelets Armein Z.R. Langi
Journal of Engineering and Technological Sciences Vol. 40 No. 2 (2008)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.eng.sci.2008.40.2.1

Abstract

This  paper  presents  a  new  model  of  linear  predictive  coding  (LPC) excitation  using  wavelets  for  speech  signals.   The  LPC  excitation   becomes  a linear combination of a set of self-  similar, orthonormal, band-pass signals with time localization and constant bandwidth in a logarithmic scale. Thus, the set of the  coefficients  in  the  linear  combination  represents  the  LPC  excitation.  The discrete  wavelet  transform  (DWT)  obtains  the  coefficients,  having  several asymmetrical  and  non-uniform  distribution  properties  that  are  attractive  for speech processing and compression. The properties include magnitude dependent sensitivity, scale dependent sensitivity, and limited frame length, which can be used  for  having  low  bit-rate  speech.  We  show  that  eliminating  8.97%  highest magnitude  coefficients  degrades  speech  quality  down  to  1.49dB  SNR,  while eliminating  27.51%  lowest  magnitude  coefficient  maintain  speech  quality  at  a level of 27.42 dB SNR. Furthermore eliminating 6.25% coefficients located at a scale associated with 175-630 Hz band severely degrades speech quality down to 4.20 dB SNR. Finally, our results show that optimal frame length for telephony applications is among 32, 64, or 128 samples.
Analysis of Input and Output Ripples of PWM AC Choppers Pekik Argo Dahono; Dessy Amirudin; Arwindra Rizqiawan; Deni Deni
Journal of Engineering and Technological Sciences Vol. 40 No. 2 (2008)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.eng.sci.2008.40.2.2

Abstract

This paper presents an analysis  of input and output ripples of PWM AC  choppers.  Expressions  of  input  and  output  current  and  voltage  ripples  of single-phase PWM AC choppers are first derived. The derived expressions are then  extended  to  three-phase  PWM  AC  choppers.  As  input  current and  output voltage ripples specification alone cannot be used to determine the unique values of inductance and capacitance of the LC filters, an additional criterion based on the  minimum reactive  power  is  proposed.  Experimental results  are included  in this paper to show the validity of the proposed analysis method.
Approximation of Hydrogen Induced Delayed Fracture of Overlaid Cladding in Pressure Vessels Steel Structure Ronnie H. Rusli; T. Fujita
Journal of Engineering and Technological Sciences Vol. 40 No. 2 (2008)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.eng.sci.2008.40.2.3

Abstract

Distribution and electronic states of interstitial hydrogen atoms in the iron lattice are discussed in regard to their influence to the lattice bonding, and theory of hydrogen induced delayed fracture of steel based upon it is proposed. Characteristics of delayed fracture are accordingly well accounted for.
Comparison of Eight Month Coastal Polluted Porcelain and Epoxy Resin Outdoor Insulators Waluyo Waluyo; Ngapuli I. Sinisuka; Parouli M. Pakpahan; Suwarno Suwarno; Maman A. Djauhari
Journal of Engineering and Technological Sciences Vol. 40 No. 2 (2008)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/itbj.eng.sci.2008.40.2.4

Abstract

This study  presents the experimental results of eight months naturally coastal polluted outdoor porcelain  and  epoxy resin  insulators. The experiments were leakage current and applied high voltage measurements used a two-channel storage  digital  oscilloscope,  in  the  hermetically  sealed  chamber,  where temperature,  humidity ,  pressure  and  applied  voltage  could  be  adjusted  and measured simultaneously. The leakage current waveforms were analyzed using FFT  and  the  relation  to  environmental  parameters  were  analyzed  using correlation  matrix  of  multivariate  statistical  tools.  It  was  also  conducted  SEM and EDAX tests. Base  on  the  correlation  coefficient  matrix, the humidity  contributed  to  leakage current  amplitude  and  phase  angle  on  the  porcelain  insulator   were  very significant,  with  the  correlation  coefficient  were  0.60  and  -0.68  respectively. Whereas,  on  polluted  epoxy  resin  insulator,  the  humidity  did  not  influence  to leakage  current  and  phase  angle  considerably.  Generally,  the  surface  became rougher than  the new one. The most three  chemical elements in pollutants  were chlorine, silicon and ferrum.

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