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IPTEK The Journal for Technology and Science
Published by Institut Teknologi Sepuluh Nopember Surabaya
ISSN : 08534098     EISSN : 20882033     DOI : -
Core Subject : Science,
Computer Science & IT
IPTEK The Journal for Technology and Science (eISSN: 2088-2033; Print ISSN:0853-4098), is an academic journal on the issued related to natural science and technology. The journal initially published four issues every year, i.e. February, May, August, and November. From 2014, IPTEK the Journal for Technology and Science publish three times a year, they are in April, August and December in online version.
Arjuna Subject : -
Articles 4 Documents
 1 
Search results for , issue "Vol 19, No 1 (2008)" : 4 Documents clear
Development of Ultra-Carbon Steel Prepared by Mechanical Alloying and Subsequent Hot Pressing Nurul T. Rochman; H. Sueyoshi
IPTEK The Journal for Technology and Science Vol 19, No 1 (2008)
Publisher : IPTEK, LPPM, Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j20882033.v19i1.158

Abstract

It is known that the most effective way to improve mechanical properties of steels is by microstructural refinement. Iron and graphite powders mixture with hypoeutectoid composition were mechanically alloyed (MAed) and subsequently hot pressed (HPed) to provide steels with fine structure. Mechanical Alloying (MA) was carried out using a planetary ball mill for 100, 200 and 300 h, while HP at 41 MPa at various temperatures: 610ºC (below), 730ºC (near) and 800ºC (above the eutectoid transformation point A1). The mechanically alloyed (MAed) powders were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM). While, the HPed compacts were characterized by SEM, Vickers hardness and tensile test. During MA, refinement of crystallite, formations of super-saturated iron solid solution and Fe/C amorphous phase occured first. With further MA time, these phases might begin to transform to more stable phases such as carbides. In the case of HP at 610ºC (below A1), very fine cementites were precipitated in fine ferrite grain with sub-micron meter in the size. However, the mechanical properties cannot be attained because of low sinterability. At 730ºC (near A1), the strength reaches the maximum value. With further temperature increase (at 800ºC), the sintering progressed well and the coarsening occured, resulting the decrease in strength. However, the fracture strain increased significantly. The steels obtained in the present study had mechanical properties comparable to those of standard (JIS) steels through the welle stablished heat treatment such as normalizing and thermal refining.
Element Size Effects in Nonlinear Analysis of Reinforced Concrete Beams without Web Reinforcement Tavio Tavio
IPTEK The Journal for Technology and Science Vol 19, No 1 (2008)
Publisher : IPTEK, LPPM, Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j20882033.v19i1.159

Abstract

A new approach is developed to the nonlinear analysis of reinforced concrete beams without stirrups subjected to a monotonically increasing loading from zero up to the ultimate load. The softening effect of concrete in tensioncompression, the tension-stiffening and tension-softening of concrete in tension are all taken into account in the proposed model. The effect of finite element mesh size is investigated by applying the crack band theory (Bazant and Oh, 1983) and taking into account the plastic strain of concrete under tension. A simple procedure for calculating the stressstrain curve of plain concrete under tension was developed and implemented into the nonlinear finite element formulation. The proposed model gives relatively good agreement with the experimental results.
Isolation of Molds for Reducing the Color of Vinase Kurniawan, Yahya; S. M., Hendro
IPTEK The Journal for Technology and Science Vol 19, No 1 (2008)
Publisher : IPTEK, LPPM, Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j20882033.v19i1.160

Abstract

Vinase or ethanol slop is blackish brown liquid, which is not friendly to the environment. Therefore, it is necessary the possibility to reduce the color biologically. The study was started by isolating molds from the vinase of Jatiroto Alcohol factory and the isolated molds was tested to study the capability of their color reduction. The results showed that there were 4 kinds of molds in the vinase i.e. : Rhizopus sp., Penicillium A, Penicillium B, and Aspergillus. Amongst these molds, Penicillium A and Penicillium B had the best potency in reducing the slop color. Around 54 % of its absorbency value at 420 nm could be reduced by the molds.
Simulation of Gas-Solid-Liquid Flow in Membrane Bioreactor Submerged Palupi, A. E.; Harahap, A. H.; Meydita, A. D.; Winardi, S.; Altway, A.
IPTEK The Journal for Technology and Science Vol 19, No 1 (2008)
Publisher : IPTEK, LPPM, Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j20882033.v19i1.155

Abstract

Hydrodynamics characteristic for the mixing of gas-solid-liquid in membrane bioreactor submerged (MBRs) and its influence on mass transfer was studied computationally at various solid concentration, incoming gas rate, and the baffle distance. Computational method was conducted by using software GAMBIT 2.1.6. for the making of the grid which represents the calculation domain and conduct the simulation using CFD software FLUENT commercial code 6.2.16. The calculation result was recorded after the iteration reach the certain convergence level. Multiphase flow in reactor was simulated with mixture model, while to model the turbulence characteristic of the flow standard k-ε model was used. The geometric system studied is bioreactor in the form of box with flat bottom, 2 baffles, submerged hollow fiber membrane and air passage at the bottom of the reactor. For the membrane modeling, it is used two approaches that is membrane as black box and membrane as porous media. The liquid used is water, and the solid is activated sludge, and air acts as gas phase. The result indicates that gas-solidliquid system with the nearest baffle location from the membrane cause, the liquid dispersion process goes faster, so that fluid in the tank can be mixed perfectly and it can increase the gas-liquid mass transfer rate and the flux at MBRs. The increase of the solid concentration does not significantly affect the change of gas-liquid mass transfer rate and flux through the membrane, but the increase of air flow rate can increase the gas-liquid mass transfer and the flux. Porous media approach give the prediction of the gas hold up distribution more over all than black box approach. The position of baffle 9 cm from tank wall is the best position viewed from the balance between the of air flow with the circulating fluid flow. Considered from the solid distribution, double inlet MBRs is better compared to that of single inlet. Flux obtained does not show significant difference. From both approaches of the membrane model, membrane model as porous media give the simulation results closer to the experimental data.

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