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Journal of Engineering and Technological Sciences

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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 â€“ 2012) Proceedings ITB on Engineering Science (2003 - 2007) Proceedings ITB (1961 - 2002)

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Articles 1,267 Documents

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Comparison Study of Flow in a Compound Channel: Experimental and Numerical Method Using Large Eddy Simulation SDS-2DH Model Eka Oktariyanto Nugroho; Syunsuke Ikeda
Journal of Engineering and Technological Sciences Vol. 39 No. 2 (2007)
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.2007.39.2.1

Flow modeling in a compound channel is a complex matter. Indeed, due to the smaller velocities in the floodplains than in the main channel, shear layers develop at the interfaces between two stage channels, and a momentum transfer corresponding to this shear layer affects the channel conveyance. Since a compound channel is characterized by a deep main channel flanked by relatively shallow flood plains, the interaction between the faster fluid velocities in the main channel and the slower moving flow on the floodplains causes shear stresses at their interface which significantly distort flow and boundary shear stress patterns. The distortion implies that flow field in rivers is highly non homogeneous turbulent, which lateral transport of fluid momentum and suspended sediment are influenced by the characteristics of flow in rivers. The nature of mechanism of lateral transport needs to be understood for the design of river engineering schemes that rely upon realistic flow. Furthermore, the flows in river are also almost turbulent. This means that the fluid motion is highly random, unsteady, and three -dimensional. Due to these complexities, the flow cannot be properly predicted by using approximate analytical solutions to the governing equations of motion. With the complexity of the problems, the solution of turbulent is simplified with mathematics equation. The momentum transfer due to turbulent exchanges is then studied experimentally and numerically. Experimental data is obtained by using ElectroMagnetic Velocimetry and Wave Height Gauge. The Large Eddy Simulation Sub Depth Scale (LES SDS)-2 Dimensional Horizontal (2DH) Model is used to solve the turbulent problem. Successive Over Relaxation (SOR) method is employed to solve the numerical computation based ob finite difference discretization. The model has been applied to the compound channel with smooth roughness. Some organized large eddies were found in the boundary between main channel and flood channel. At this boundary the transverse velocity profile exhibits a steep gradient, which induces significant mass and momentum exchange, acts as a source of vorticity, and generates high Reynolds stresses. The Large Eddy Simulation SDS-2DH model enables to predict quite successfully the wavelength of some observed vortices. The estimated vortex wavelengths agree again with the measurements and the theoretical predictions. The present model is proven to be a useful tool for engineering applications, as it can simulate the dynamic development of large eddies.

Experimental Study of an Aluminum-Polysilicon Thermopile for Implementation of Airflow Sensor on Silicon Chip Ayub Subandi; Irman Idris; Adang Suwandi Ahmad
Journal of Engineering and Technological Sciences Vol. 39 No. 2 (2007)
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.2007.39.2.2

A multi-directional airflow sensor has been realized. The essential part of the considered sensor is a thermopile configuration, which enables the measurement of flow speed and flow direction. The thermopile is a series arrangement of eight thermocouples. A thermocouple converts a difference in temperature into an electrical signal, by means of the Seebeck effect . The thermocouples are made of aluminum-N-type polysilicon junctions. The incoming flow is heated and the degree of heat transfer by convection to the flow, depends on the speed of the flow; the faster the flow the smaller the heat transfer, which leads to a smaller (Seebeck) output voltage of the thermopiles. After signal conditioning - i.e., filtering and amplification by means of an amplification system - the electrical output signals of the thermopiles are further signal-processed by applying analog-to-digital signal conversion, so that finally the flow speed and the flow direction can be properly displayed on a computer screen. The measured values of the Seebeck coefficient or thermopower (S) were in the range of: 0.43 to 0.68 mV/K which are in good agreement with the values found in the literature: 0.5 to 0.7 mV/K. Moreover, it was found that the flow speed Uï‚¥ is proportional to the reciprocal value of the square of the output voltage of the outgoing thermopile.

Utilizing Shear Factor Model and Adding Viscosity Term in Improving a Two-Dimensional Model of Fluid Flow in Non Uniform Porous Media Yazid Bindar; IGBN Makertihartha; M. Dani Supardan; Luqman Buchori
Journal of Engineering and Technological Sciences Vol. 39 No. 2 (2007)
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.2007.39.2.3

In a packed bed catalytic reactor, the fluid flow phenomena are very complicated because the fluid and solid particle interactions dissipate the energy. The governing equations were developed in the forms of specific models. The shear factor model was introduced in the momentum equation for covering the effect of flow and solid interactions in porous media. A two dimensional numerical solution for this kind of flow has been constructed using the finite volume method. The porous media porosity was treated as non-uniform distribution in the radial direction. Experimentally, the axial velocity profiles produce the trend of having global maximum and minimum peaks at distance very close to the wall. This trend is also accurately picked up by the numerical result. A more comprehensive shear factor formulation results a better velocity prediction than other correlations do. Our derivation on the presence of porous media leads to an additional viscosity term. The effect of this additional viscosity term was investigated numerically. It is found that the additional viscosity term improves the velocity prediction for the case of higher ratio between tube and particle diameters

Root Locus Based Autopilot PIDâs Parameters Tuning for a Flying Wing Unmanned Aerial Vehicle Fendy Santoso; Ming Liu
Journal of Engineering and Technological Sciences Vol. 40 No. 1 (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.2008.40.1.2

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

Application of Wavelet LPC Excitation Model for Speech Compression Armein Z.R. Langi
Journal of Engineering and Technological Sciences Vol. 40 No. 1 (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.2008.40.1.1

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; S. K. Ardianto
Journal of Engineering and Technological Sciences Vol. 40 No. 1 (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.2008.40.1.3

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 Collectorâs Configuration for an Ejector-Refrigeration Cycle Raffles Senjaya; I Made Astina
Journal of Engineering and Technological Sciences Vol. 40 No. 1 (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.2008.40.1.4

Solar collectorâs 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.

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

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

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

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.

Page 61 of 127 | Total Record : 1267

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