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Journal of Engineering and Technological Sciences

JETS
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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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Prediction Model of Coal and Gas Outburst Based on Rough Set-Unascertained Measure Theory Gong, Weidong
Journal of Engineering and Technological Sciences Vol 50, No 6 (2018)
Publisher : ITB Journal Publisher, LPPM ITB

This paper proposes a risk evaluation model based on rough sets (RS) and the unascertained measure theory (UMT) for solving the accuracy problem of coal and gas outburst prediction with the aim to reduce economic losses and casualties in coal mining. The coal and gas outburst prediction problem is constrained by the selection of the prediction indexes, the coupling of a single index, and the weight of each index. The proposed RS-UMT model applies two modified techniques. The first one is a method for index weight determination that was improved by rough set theory. The second one is a method for coupling a single index that was modified by the unascertained measure theory. The RS-UMT model not only well solves the problem of coupling a single index of coal and gas outbursts, but also solves the problem that the weight is susceptible to subjective factors and prior knowledge. The RS-UMT model was used to judge the risk degree of outburst of 10 mining faces in the Pingdingshan No. 8 Mine and No. 10 Mine. The predictive results of the model were basically identical to the actual measured results. The performance of the RS-UMT model was also compared to existing methods. Based on the case study it can be concluded that the RS-UMT model is an accurate and very promising method for solving the coal and gas outburst prediction problem.

Shelf-life Evaluation of Packaged Fermented Cassava Flour Lestari, Dianika; Liandro, Yessica; Ang, Elvina; Kresnowati, M.T.A. Penia
Journal of Engineering and Technological Sciences Vol 51, No 1 (2019)
Publisher : ITB Journal Publisher, LPPM ITB

Cassava is a carbohydrate source with high productivity per hectare of plantation. Cassava is made into flour to extend its shelf life. However, traditional flour still has low quality due to its yellowish color and distinct odor. Fermented cassava flour (FERCAF) is produced by fermentation of cassava chips in a circulated retting fermenter by using a combination of Lactobacillus plantarum, Bacillus subtilis, and Aspergillus oryzae, followed by drying and milling. This process has been used successfully to produce flour with a white color and a neutral aroma. To enable industrial scale production and market introduction, the quality deterioration and shelf life of packaged FERCAF should be determined. The objective of this research was to investigate the effect of storage time and packaging type on the physicochemical properties and to determine shelf life of packaged FERCAF. FERCAF was stored in a controlled-incubator over 94 days using two packaging types: LDPE plastic and kraft paper. Based on the result, the number of microorganisms over 94 days of storage was within safe limits. The average estimated shelf life of packaged FERCAF was in the range of 3-4 months at ambient temperature. The shelf life of FERCAF packaged in LDPE plastic was approximately 15 days longer than that packaged in kraft paper.

Performance Enhancement by Using Wet Pad in Vapor Compression Cooling System Zaidan, Maki H.; Ibrahim, Thamir K.; Alkumait, Aadel A. R.
Journal of Engineering and Technological Sciences Vol 51, No 1 (2019)
Publisher : ITB Journal Publisher, LPPM ITB

Vapor compression cooling systems are widely used in hot and dry climates where the atmospheric temperature in summer reaches around 48 °C and the relative humidity can be below 20%. These cooling systems normally use environmentally friendly gases that do not harm the ozone layer. These systems work with high gas pressure, which consumes high energy and leads to a low coefficient of performance when compared to cooling systems that do not use an environmentally friendly gas. Theoretical and experimental studies have been conducted to find a suitable solution for the performance improvement of this type of cooling system. A possible solution is to lower the temperature of the air before it enters the condenser of the compression cooling system by passing it through a wet pad. The water evaporates due to the latent heat that is withdrawn from the wet pad. The air temperature is reduced to about 11 °C before it enters the condenser of the compression cooling system. This enhancement increases the cooling capacity of the vapor compression cycle by nearly 20% and increases the coefficient of performance by 15%, in addition to reducing the consumed electricity up to 15%. In conclusion, the proposed method of adding a wet pad can significantly enhance the performance of the vapor compression cooling system.

Study on the Mechanism of Particle Breakage under New Composite Loads Li, Zhanfu; Ye, Yiqing; Tong, Xin; Li, Kunyuan
Journal of Engineering and Technological Sciences Vol 51, No 2 (2019)
Publisher : ITB Journal Publisher, LPPM ITB

A theoretical model of particle breakage under a novel combination of dynamic and static loads is presented in this paper. In order to enhance the capability of the actual physical and mechanical properties towards rocks, parallel connector parameters of a bonded particle model (BPM) from the discrete element method (DEM) were investigated by uniaxial compression tests. Then, the efficiency evaluation index system of particle breakage was defined and different simulations of various parameters were set, i.e. the speed of the moving plate, the curvature of the moving plate, the curvature of the fixed plate, the space between the two plates, and the initial particle radius. The mechanism of particle breakage was analyzed by the relationships between the efficiency evaluation index and various parameters. The investigation of particle breakage theory and law can help to design and improve crushing equipment, reduce the energy consumption of the crusher, and improve the quality of the broken product.

Performance Analysis of Energy Storage in Smart Microgrid Based on Historical Data of Individual Battery Temperature and Voltage Changes Haq, Irsyad Nashirul; Kurniadi, Deddy; Leksono, Edi; Yuliarto, Brian; Soelami, F.X. Nugroho
Journal of Engineering and Technological Sciences Vol 51, No 2 (2019)
Publisher : ITB Journal Publisher, LPPM ITB

In this work, a historical data based battery management system (BMS) was successfully developed and implemented using an embedded system for condition monitoring of a battery energy storage system in a smart microgrid. The performance was assessed for 28 days of operating time with a one-minute sampling time. The historical data showed that the maximum temperature increment and the maximum temperature difference between the batteries were 4.5 °C and 2.8 °C. One of the batteries had a high voltage rate of change, i.e. above 3.0 V/min, and its temperature rate of change was very sensitive, even at low voltage rate of changes. This phenomenon tends to indicate problems that may deplete the battery energy storage system’s total capacity. The primary findings of this study are that the voltage and temperature rates of change of individual batteries in real operating conditions can be used to diagnose and foresee imminent failure, and in the event of a failure occurring the root cause of the problem can be found by using the historical data based BMS. To ensure further safety and reliability of acceptable practical operating conditions, rate of change limits are proposed based on battery characteristics for temperatures below 0.5 °C/min and voltages below 3.0 V/min.

Borehole Microseismic Imaging of Hydraulic Fracturing: A Pilot Study on a Coal Bed Methane Reservoir in Indonesia Ry, Rexha Verdhora; Septyana, Tepy; Widiyantoro, Sri; Nugraha, Andri Dian; Ardjuna, Arii
Journal of Engineering and Technological Sciences Vol 51, No 2 (2019)
Publisher : ITB Journal Publisher, LPPM ITB

Over the last decade, microseismic monitoring has emerged as a considerable and capable technology for imaging stimulated hydraulic fractures in the development of unconventional hydrocarbon resources. In this study, pilot hydraulic-fracturing treatments were operated at a coal-bed methane (CBM) field in Indonesia to stimulate the flow and increase the reservoir’s permeability while the monitoring system was set in a single near-vertical borehole. Locating event sources accurately is fundamental to investigating the induced fractures, but the geometry of a single downhole array is a challenging data processing task, especially to remove ambiguity of the source locations. The locating procedure was reviewed in 3 main steps: (i) accurate picking of P- and S-wave phases; (ii) inclusion of P-wave particle motion to estimate the back azimuth; (iii) guided inversion for hypocenter determination. Furthermore, the seismic-source moment magnitudes were calculated by employing Brune’s model. Reliable solutions of locations were obtained as shown statistically by uncertainty ellipsoids and a small misfit. Based on our results, both induced and triggered seismicity could be observed during the treatments and therefore conducting intensive monitoring is important. The triggered seismicity is an undesired activity so disaster precautions need to be taken, in particular for preventing reactivation of pre-existing faults.

Prestressed Concrete I-Girder Optimization via Genetic Algorithm Adibaskoro, Tito; Suarjana, Made
Journal of Engineering and Technological Sciences Vol 51, No 2 (2019)
Publisher : ITB Journal Publisher, LPPM ITB

Prestressed concrete has been gaining popularity in the construction industry because of its many advantages, which include reduced dead load due to less material used and overall cost savings. Nonetheless, a single prestressed concrete I-girder as a structural element in highway bridges is still significantly costly and massive, so optimization can yield a significant amount of cost savings as well as reduced material consumption. In this study, prestressed concrete I-girder optimization was carried out by implementing a genetic algorithm (GA), a method inspired by nature’s evolution and natural selection. This study evaluates a number of aspects of applying a genetic algorithm for optimization of material cost of a prestressed concrete I-girder design. A new method for calculating the fitness value is proposed, which was proven to be essential for the application developed in this study. The best solution that resulted from the optimization process is presented, defined by being the least costly solution while still maintaining compliance with the AASHTO LRFD 2007 design code, which includes ultimate strength, service stresses and deflection, detailing requirements, geometrical feasibility, etc. Lastly, a sensitivity analysis was carried out, discussing the influence of the starting conditions on the output of the optimization process.

Alkaline-assisted Microwave Pretreatment of Tetraselmis suecica Biomass for Fed-batch Enzymatic Hydrolysis Kassim, Mohd Asyraf; Meng, Tan Kean; Serri, Noor Aziah
Journal of Engineering and Technological Sciences Vol 51, No 2 (2019)
Publisher : ITB Journal Publisher, LPPM ITB

A two-part study on pretreatment and fed-batch enzymatic hydrolysis of pretreated Tetraselmis suecica using a high initial biomass concentration was conducted. First, the effect of different pretreatment processes, i.e. microwave (MC), dilute alkaline (AK), and microwave-alkaline assisted (MAK) pretreatment, on enzymatic hydrolysis of T. suecica biomass was evaluated. Furthermore, high initial biomass concentration enzymatic hydrolysis improvement via a fed-batch strategy was performed. Among the pretreatments tested, the MAK pretreatment produced the highest sugar concentration at 9.83 ± 0.24 mg/mL, corresponding to a conversion yield of up to 85.58% of carbohydrate content available in the pretreated biomass. The solid fraction generated after pretreatment was characterized using Fourier transform infrared (FTIR) spectroscopy. The FTIR analysis revealed a significant change in the functional hydroxyl and acetyl groups of the biomass, which is favorable for enzymatic hydrolysis. Introducing an initial microalgal biomass concentration beyond 15% (w/v) exhibited a low enzymatic hydrolysis yield. The fed-batch enzymatic hydrolysis strategy of the MAK pretreated T. suecica was further investigated by adding the substrate at different time intervals. The findings indicate that the fed-batch operation system could enhance sugar production and enzymatic hydrolysis yield one-fold.

A Coal Mine Underground Localization Algorithm Based on the Feature Vector Yinjing, Guo; Xianqi, Song; Lei, Yang; Wenhong, Lv
Journal of Engineering and Technological Sciences Vol 51, No 2 (2019)
Publisher : ITB Journal Publisher, LPPM ITB

To enhance the position estimation accuracy of an underground localization system for coal mine roadways, an algorithm based on the feature vector of received signals is presented in this paper. The algorithm includes three steps: the construction process of a feature vector database and a distance database, the vector matching process and the localization process. When a signal vector is received, it only needs to calculate the distance from the received vector to the center vector of each subset and then compare it with the data in the distance database. After multiple filtering and comparing the source of the strongest signal, the coordinates closest to the received vector are found. The experiment showed that the maximum error of this algorithm was 4 m and the average error was 1.62 m. Furthermore, within a localization error of 1 m, the X-axis localization accuracy was 98% while the Y-axis localization accuracy was 86%. Also, the algorithm took much less time compared to the KNN and WKNN algorithms, so the algorithm meets the requirements of coal mine safety systems and underground personnel localization systems.

An Analysis of EEG Changes during Prolonged Simulated Driving for the Assessment of Driver Fatigue Zuraida, Rida; Iridiastadi, Hardianto; Sutalaksana, Iftikar Zahedi; Suprijanto, Suprijanto
Journal of Engineering and Technological Sciences Vol 51, No 2 (2019)
Publisher : ITB Journal Publisher, LPPM ITB

Fatigue during driving is the main contributing factor to road accidents. It is influenced by time on task (TOT) and time of day (TOD). Recent electroencephalogram (EEG) research on fatigue assessment has shown a promising result in explaining the fatigue phenomenon. However, different findings exist regarding the best EEG parameters related to fatigue. This study examined EEG changes according to the effect of TOT and TOD and determined the best parameters to distinguish fatigue status. To generate driver fatigue, prolonged driving in the morning and at night in a simulator was conducted. The EEG signal was collected from 28 male participants at frontal and occipital areas. The EEG power (brainwave) was determined from the first and last 5 minutes of the driving task and after a break of 30 minutes. The results of this study showed a general tendency of EEG power changing throughout the driving sessions. However, changes related to fatigue were only found for the night sessions, as confirmed by q power and the subjective fatigue measurement result. This study showed that TOT (as a factor that induces fatigue) was explained by q from the frontal area, whereas TOD was differentiated by a, q, q/b, (q+a)/b and (q+a)/(b+a).

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