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INDONESIA
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 1 (2008)" : 4 Documents clear
Application of Wavelet LPC Excitation Model for Speech Compression Langi, Armein Z.R.
Journal of Engineering and Technological Sciences Vol 40, No 1 (2008)
Publisher : ITB Journal Publisher, LPPM ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (233.045 KB) | DOI: 10.5614/itbj.eng.sci.2008.40.1.1

Abstract

This paper presents an application of linear predictive coding (LPC) excitation wavelet models for low bit- rate, high-quality speech compression. The compression scheme exploits the model properties, especially magnitude dependent sensitivity, scale dependent sensitivity, and limited frame length. We use the wavelet model in an open-loop dither based codebook scheme. With t his approach, the compression yields a signal-to-noise ratio of at least 11 dB at rates of 5 kbit/s and.
Leakage Current Waveforms and Arcing Characteristics of Epoxy Resin for Outdoor Insulators under Clean and Salt Fogs Suwarno, Suwarno; Ardianto, S. K.
Journal of Engineering and Technological Sciences Vol 40, No 1 (2008)
Publisher : ITB Journal Publisher, LPPM ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (526.468 KB) | DOI: 10.5614/itbj.eng.sci.2008.40.1.3

Abstract

Ceramic  outdoor  insulators  have  been  used  in  high  voltage transmission lines since long time ago. Due to superiority in their resistance to pollution, recently, polymeric outdoor insulators are widely used. Epoxy resin is one  polymer  which  shows  good  properties  for  outdoor  insulation.  During service,  outdoor  insulators  may severe a certain degree of pollution  which may reduce  their  surface  resistance.  Leakage  current  (LC)  usually   increase  and degradation  may  take  place.  This  paper  reports  experimental  results  on  the leakage current  waveforms and arcing characteristics of epoxy resin  under clean and salt fog. The samples used are blocks of epoxy resin with dimension of 250 x  50  x  20  mm3 .  The  samples  were  put  in  a  test  chamber  with  dimension  of 900x900x1200 mm3 with controllable humidity  and pollution conditions. Clean and  salt  fog  were  generated  according  to  IEC  60-1  and  507.  The  arcing experiment  was  done  with  incline  plane  test  in  accordance  with  IEC  587.  AC voltage  in the range from 5 kV to 50 kV with frequency of 50 Hz  was applied. The LC waveforms  up to flash over  were measured. The magnitudes as well as harmonic  content  of  the  LC  were  analyzed.   The  correlation  between  LC waveforms  and  dry  band  arching  phenomenon  was  elaborated.  Visual observation  of  the  arc  on  the  sample  surfaces  was  observed  using  a  video camera. Experimental results indicated that LC magnitude on clean  samples was slightly affected by humidity (RH). However, under salt fog, RH greatly affected the LC magnitude. The flashover voltage of clean samples under salt fog reduced significantly  for  fog  conductivity  of  more  than  1.2  mS/cm.  Kaolin-polluted samples under salt fog showed an Ohmic behaviour. The LC magnitude was high and a large discrepancy of LC magnitude was observed for high applied voltage of  larger  than  25  kV.  The  largest  LC  magnitude  was  observed  on  salt-kaolin polluted samples under clean fog at high RH. LC waveforms analysis indicated that in general LC waveforms were distorted from sinusoidal. For clean samples under clean fog, THD  of LC decreased with RH but slightly increased with the applied voltage. Large distortion at the peak of LC waveform  was observed on kaolin  polluted  sample  under  salt  fog  of  3.6  mS/cm  and  high  RH  and  high applied voltage. This correlates with corona arc on the sample surface. Similar behaviour  was  observed  on  kaolin-salt  polluted  samples  under  clean  fog. Tracking arc experiment indicated that arc length LC magnitude and arc intensity increased with the pollutant conductivity. The THD also significantly increased with  pollutant  conductivity.  At  conductivity  of  less  than  0.6  mS/cm  the unsymmetrical  LC  waveforms  were  obtained.  However,  symmetrical  LC waveforms were observed for conductivity of 0.9 and 1.2 mS/cm. The change of LC magnitude and waveform at different condition of samples may be useful for the diagnostics of insulator condition.
Comparative Study on Solar Collector’s Configuration for an Ejector-Refrigeration Cycle Senjaya, Raffles; Astina, I Made
Journal of Engineering and Technological Sciences Vol 40, No 1 (2008)
Publisher : ITB Journal Publisher, LPPM ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (434.828 KB) | DOI: 10.5614/itbj.eng.sci.2008.40.1.4

Abstract

Solar collector’s configuration plays important role  on solar-powered refrigeration systems  to work as heat source for generator . Three types of solar collector consisting  of flat plate, evacuated tube, and compound parabolic solar collectors  are  compared  to  investigate  their  performances.  The  performances consist of the behavior of heat which can be absorbed by the collectors, heat loss from  the  collectors  and outlet temperature of working fluid at several slopes of the  solar  collectors.  The  new  accurate  analysis  method  of  heat  transfer  is conducted  to  predict  the  performance  of  the  solar  collectors.  The  analysis  is based  on  several  assumptions,  i.e.  sky  condition  at  Bandung  is  clear  and  not raining from 08.00 until 17.00 and thermal resistance at cover and absorber plate is  negligible. The numerical calculation results confirm that performance of  the evacuated  tubes  solar  collector  at  the  same  operating  conditions  is higher  than the  others.  For  the  case  of  an  evacuated-tubes  solar  collector  system  with aperture area of 3.5 m2, the maximum heat which can be absorbed is 3992  W for the highest solar intensity  of  970 W/m2 at 12.00  with  horizontal position of  the solar  collector.  At  this  condition,  the  highest  outlet  temperature  of  water  is 347.15 K with mass flow rate 0.02 kg/s and inlet temperature 298 K.
Root Locus Based Autopilot PID’s Parameters Tuning for a Flying Wing Unmanned Aerial Vehicle Santoso, Fendy; Liu, Ming
Journal of Engineering and Technological Sciences Vol 40, No 1 (2008)
Publisher : ITB Journal Publisher, LPPM ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (500.091 KB) | DOI: 10.5614/itbj.eng.sci.2008.40.1.2

Abstract

This paper depicts the applications of classical root locus based PID control to the longitudinal flight dynamics of a Flying Wing Unmanned Aerial Vehicle, P15035, developed by Monash Aerobotics Research Group in the Department of Electrical and Computer Systems Engineering, Monash University, VIC, Australia. The challenge associated with our UAV is related to the fact that all of its motions and attitude variables are controlled by two independently actuated ailerons, namely elevons, as its primary control surfaces along with throttle, in contrast to most conventional aircraft which have rudder, aileron and elevator. The reason to choose PID control is mainly due to its simplicity and availability. Since our current autopilot, MP2028, only provides PID control law for its flight control, our design result can be implemented straight away for PID parameters’ tuning and practical flight controls. Simulations indicate that a well-tuned PID autopilot has successfully demonstrated acceptable closed loop performances for both pitch and altitude loops. In general, full PID control configuration is the recommended control mode to overcome the adverse impact of disturbances. Moreover, by utilising this control scheme, overshoots have been successfully suppressed into a certain reasonable level. Furthermore, it has been proven that exact pole-zero cancellations due to derivative controls in both pitch and altitude loop to eliminate the effects of integral action -contributed by open loop transfer functions of elevon-average-to-pitch as well as pitch-to-pitch-rate- is impractical

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