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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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An LMI Approach to Hâ Performance Analysis of Continuous-Time Systems with Two Additive TimeVarying Delays Ridwan, Wrastawa; Trilaksono, Bambang Riyanto
Journal of Engineering and Technological Sciences Vol 43, No 2 (2011)
Publisher : ITB Journal Publisher, LPPM ITB

ThisÂ paperÂ investigatesÂ theÂ problemÂ ofÂ Hâ performanceÂ analysisÂ for continousâtime systems with two additive time -varying delays in the state.Â Our objective is focused onÂ stabilityÂ analysis ofÂ aÂ continuousÂ system with two timevaryingÂ delaysÂ withÂ anÂ Hâ disturbanceÂ attenuationÂ levelÂ Î³.Â ByÂ exploiting Â Lyapunov-Krasovski functional and introducing free weighting matrix variables, LMI stability condition have been derived.

Potential Risk Analysis of Tailings Dam under Preloading Condition and Its Countermeasures Wang, Shuren; Zhang, Haiqing; Zou, Zhengsheng; Wang, Ping; Yu, Tao
Journal of Engineering and Technological Sciences Vol 47, No 1 (2015)
Publisher : ITB Journal Publisher, LPPM ITB

It is very important for mine production safety to ensure the stability of the tailings dam. Taking a flatland tailings pond as the background, a threedimensionalÂ computational model was built based on aÂ tailings dam under mullock heapÂ preloading condition. ConsideringÂ the current operatingÂ water level conditions, a liquid-solid coupling analysis of the model was conducted.The deformation characteristics of the tailings dam were revealed during successive preloading at the front of the dam. The safety factor and the potential slide face of the tailings dam were calculated under different conditions using the strength reduction method. The results show that the tailings dam in its current condition is basically stable, but if the mullock heap continues to be heightened, the tailings dam will become unstable. Therefore, in order to limit the height of the mullock heap, establishing a monitor and early warning mechanism are put forward to ensure mine production safety.

Experimental Study of Confined Low-, Medium- and High-Strength Concrete Subjected to Concentric Compression Antonius, Antonius; Imran, Iswandi
Journal of Engineering and Technological Sciences Vol 44, No 3 (2012)
Publisher : ITB Journal Publisher, LPPM ITB

AnÂ experimentalÂ studyÂ ofÂ 23Â low-,Â medium-Â andÂ high-strengthconcreteÂ columns is presented in this paper. Square-confined concrete columns withoutÂ longitudinalÂ reinforcementÂ wereÂ designed,Â andÂ testedÂ underÂ concentric axialÂ compression.Â TheÂ columnsÂ wereÂ madeÂ ofÂ concreteÂ withÂ aÂ compressive strength ranging between 30 MPa and 70 MPa. The test parameters in the study areÂ concreteÂ compressiveÂ strengthsÂ andÂ confiningÂ steelÂ properties,Â i.e.Â spacing, volumetricÂ ratiosÂ andÂ configurations.Â TheÂ effectsÂ ofÂ theseÂ parametersÂ onÂ the strengthÂ andÂ ductilityÂ ofÂ square-confinedÂ concreteÂ wereÂ evaluated.Â OfÂ the specimens tested in this study, the columns made with higher-strength concrete produced less strengthÂ enhancement and ductility than those with lower-strength concrete.Â TheÂ steelÂ configurationsÂ wereÂ foundÂ to Â haveÂ anÂ importantÂ roleÂ in governingÂ theÂ strengthÂ andÂ ductilityÂ ofÂ theÂ confinedÂ high-strengthÂ concrete. Moreover,Â severalÂ modelsÂ ofÂ strengthÂ enhancementÂ forÂ confinedÂ concrete availableÂ inÂ theÂ literatureÂ turnedÂ outÂ toÂ beÂ quiteÂ accurateÂ inÂ predictingÂ the experimental results.

Low-Cost Real-Time Gas Monitoring Using a Laser Plasma Induced by a Third Harmonic Q-Switched Nd-YAG Laser Abdulmadjid, Syahrun Nur; Kurniawan, Koo Hendrik; Lie, Tjung Jie; Lee, Yong Inn; Kitazima, Iwao; Kagawa, Kiichiro
Journal of Engineering and Technological Sciences Vol 37, No 2 (2005)
Publisher : ITB Journal Publisher, LPPM ITB

A gas plasma induced by a third harmonic Nd-YAG laser with relatively low pulsed energy (about 10 mJ) has favorable characteristics for gas analysis due to its low background characteristics, nevertheless a high power fundamental Nd-YAG laser (100-200 mJ) is widely used for laser gas breakdown spectroscopy. The air plasma can be used as a low-cost real-time gas monitoring system such that it can be used to detect the local absolute humidity, while a helium plasma can be used for gas analysis with a high level of sensitivity. A new technique using a helium plasma to improve laser ablation emission spectroscopy is proposed. Namely, the third harmonic Nd-YAG laser is focused at a point located some distance from the target in the 1-atm helium surrounding gas. By using this method, the ablated vapor from the target is excited through helium atoms in a metastable state in the helium plasma.

Root Locus Based Autopilot PIDâs 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

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 parametersâ 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

Feasibility of Recovering Energy from Municipal Solid Waste to Generate Electricity Pasek, Ari Darmawan; Gultom, Kilbergen W.; Suwono, Aryadi
Journal of Engineering and Technological Sciences Vol 45, No 3 (2013)
Publisher : ITB Journal Publisher, LPPM ITB

Population growth and economic development in Indonesia have increased the production of municipal solid waste (MSW) in many big cities, causing sanitary problems. The (MSW) disposal problem can be solved by applying an appropriate technology that can reduce the volume of the waste effectively and efficiently. Waste-to-Energy (WTE), or Energy-from-Waste (EFW), is one of the most effective and efficient technologies for reducing the waste volume. Energy recovered from the waste can be used for thermal or electricity generation. This paper deals with a feasibility study of utilizing MSW for generating electricity. A survey and investigation of waste characteristics, including waste composition, chemical and physical composition, and heating value, were carried out for typical Bandung MSW. An average heating value of 1500 kcal/kg can be expected from pre-treated MSW to be used as a fuel for direct combustion in a WTE plant. A typical design for a small-scale WTE plant is shown in this paper and also an energy analysis is provided. Approximately 800 kW of electric power can be generated from 50 tonnes of MSW per day.

Effect of Rake Angle on Stress, Strain and Temperature on the Edge of Carbide Cutting Tool in Orthogonal Cutting Using FEM Simulation Yanda, Hendri; Ghani, Jaharah A.; Che Haron, Che Hassan
Journal of Engineering and Technological Sciences Vol 42, No 2 (2010)
Publisher : ITB Journal Publisher, LPPM ITB

Demand for higher productivity and good quality for machining parts has encourage many researchers to study the effects of machining parameters using FEM simulation using either two or three dimensions version. These are due to advantages such as software package and computational times are required. Experimental work is very costly, time consuming and labor intensive. The present work aims to simulate a three-dimensional orthogonal cutting operations using FEM software (deform-3D) to study the effects of rake angle on the cutting force, effective stress, strain and temperature on the edge of carbide cutting tool. There were seven runs of simulations. All simulations were performed for various rake angles of -15 deg, -10 deg, -5 deg, 0 deg, +5 deg, +10 deg, and +15 deg. The cutting speed, feed rate and depth of cut (DOC) were kept constant at 100 m/min, 0.35 mm/rev and 0.3 mm respectively. The work piece used was ductile cast iron FCD500 grade and the cutting tool was DNMA432 series (tungsten, uncoated carbide tool, SCEA = 0; and radius angle 55 deg). The analysis of results show that, the increase in the rake angle from negative to positive angle, causing the decrease in cutting force, effective stress and total Von Misses strain. The minimum of the cutting force, effective stress and total Von Misses strain were obtained at rake angle of +15 deg. Increasing the rake caused higher temperature generated on the edge of carbide cutting tool and resulted in bigger contact area between the clearance face and the workpiece, consequently caused more friction and wear. The biggest deformation was occurred in the primary deformation zone, followed by the secondary deformation zone. The highest stress was also occurred in the primary deformation zone. But the highest temperature on the chip usually occurs in secondary deformation zone, especially in the sliding region, because the heat that was generated in the sticking region increased as the workpiece was adhered by the tool and later it was sheared in high frictional force.Â

Optimal Overhaul-Replacement Policies for Repairable Machine Sold with Warranty Soemadi, Kusmaningrum; Iskandar, Bermawi P.; Taroepratjeka, Harsono
Journal of Engineering and Technological Sciences Vol 46, No 4 (2014)
Publisher : ITB Journal Publisher, LPPM ITB

This research deals with an overhaul-replacement policy for a repairable machine sold with Free Replacement Warranty (FRW). The machine will be used for a finite horizon, T (T <ï¥), and evaluated at a fixed interval, s (s< T). At each evaluation point, the buyer considers three alternative decisions i.e. Keep the machine, Overhaul it, or Replace it with a new identical one. An overhaul can reduce the machine age virtually, but not to a point that the machine is as good as new. If the machine fails during the warranty period, it is rectified at no cost to the buyer. Any failure occurring before and after the expiry of the warranty is restored by minimal repair. An overhaul-replacement policy is formulated for such machines by using dynamic programming approach to obtain the buyerâs optimal policy. The results show that a significant rejuvenation effect due to overhaul may extend the length of machine life cycle and delay the replacement decision. In contrast, the warranty stimulates early machine replacement and by then increases the replacement frequencies for a certain range of replacement cost. This demonstrates that to minimize the total ownership cost over T the buyer needs to consider the minimal repair cost reduction due to rejuvenation effect of overhaul as well as the warranty benefit due to replacement. Numerical examples are presented for both illustrating the optimal policy and describing the behavior of the optimal solution.

Semiannual Kelvin Waves Propagation along the South Coast of Sumatra-Jawa-Bali and the Lesser Sunda Islands Observed by TOPEX/POSEIDON and ERS-1/2 Satellites Syamsudin, F.
Journal of Engineering and Technological Sciences Vol 36, No 2 (2004)
Publisher : ITB Journal Publisher, LPPM ITB

The merged TOPEX/POSEIDON (T/P) and ERS-1/2 altimeter data during 10/14/1993 â 2/12/2002 have been used to study Indian Ocean Kelvin waves propagation along the south coast of Jawa, Bali, Lombok, and the Lesser Sunda Islands. The results show that the occurrence of semiannual Indian Ocean Kelvin waves either in April/May or November/December for all the year of 1993-2001 (except in 1994) with the intraseasonal period and phase speed ranging from 35 to 90-day and 1.54 to 2.9 m/s, respectively.

Behavior of Natural Estrogens in Activated Sludge: Biodegradation in Semicontinuous Reactor under Aerobic, Anaerobic and Sequential Anaerobic/Aerobic Conditions Desmiarti, Reni; Li, Fusheng
Journal of Engineering and Technological Sciences Vol 45, No 2 (2013)
Publisher : ITB Journal Publisher, LPPM ITB

The behavior of natural estrogens was examined by separately spiking 17Î²-estradiol (E2) and estrone (E1) into semicontinuous activated sludge reactors operated under aerobic, anaerobic and sequential anaerobic/aerobic conditions. Under aerobic and anaerobic conditions, E1 was formed from E2. The cactivated sludge; biodegradation; estrogens; estradiol; estroneonversion of E1 to E2 was did not occur under aerobic conditions. The maximum conversion of E2 to E1 was higher than the maximum conversion of E1 to E2. Overall, the degradation rate of E2 (kE2) was much faster than that of E1 (kE1). The findings suggest that E1 is probably more persistent than E2 in effluent of sewage treatment plants.

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