2024-03-29T09:06:50Z
https://www.ije.ir/?_action=export&rf=summon&issue=11449
International Journal of Engineering
IJE
1025-2495
1025-2495
2011
24
3
Xylanase Production under Solid State Fermentation by Aspergillus niger
Morteza
Khanahmadi
Saideh Sadat
Shahi1
Iran
Alemzadeh
Central composite orthogonal design was applied to quantify relations of xylanase production, loss of dry matter and change of pH with four critical variables during solid state fermentation of a mixture of wheat bran and wheat straw on which Aspergillus niger CCUG 33991 was cultivated. The studied variables included the percentage of wheat straw, temperature, moisture content, and fermentation time. The second-order quadratic model predicted the xylanase activity at a suitable set of conditions namely 29°C, 55% moisture content, and 50 hours of fermentation to be 1465 U/g of fermented dry matter which differed less than 6% from measured value at this set of conditions. Furthermore, the obtained models predicted dry matter loss and pH with less than 17% error for the same conditions. The results were used for xylanase production in an intermittently mixed forcedly aerated pilot. Applicability of models for prediction of pilot scale SSF performance was investigated. The results showed considerable deviations of measured trends from model predicted ones. Presence of mixing, temperature and moisture shocks and better oxygen supply are of possible reasons of deviations.
Key words Xylanase
Solid state fermentation
pilot
Aspergillus niger
optimization
Response Surface
2011
10
01
197
208
https://www.ije.ir/article_71912_e6b2b7f3e2ef58450643a9aeceaf9736.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2011
24
3
Laboratory Studies on the Effect of Vertical Gravel Column Drains on Liquefaction Potential
Alireza
Hamedi Sangari
Seyed Morteza
Marandi
Abstract: In recent years deadly earthquakes in seismic areas have caused special concerns regarding liquefaction phenomenon by researchers and specialists. Excess pore water pressure in loose sediments may cause phenomena such as boiling, shearing strength and dynamic stiffness reduction and lateral movements cause difficulties. Many remedial methods such as soil replacement with proper materials, in situ compaction of the soil, soil improvement using in situ grouting, and column drains have been designed and used so far to overcome liquefaction phenomenon. For existing areas with liquefaction potentials and high depths, soil replacement method is generally impossible. Vertical drain method which is both economical and easy in execution can be an alternative way to be used. In this article, three series of 1-g shaking table laboratory tests were carried out and vertical column gravel drains are modeled. In the models, various importing acceleration with variation in column gravel drains distances are studied. For modeling, Anzali shore sand situated in the north of Iran was used. Results showed that the behavior of gravel column drains varies with variation in imported seismic acceleration, and the output of this method for reduction of liquefaction potential is affected considerably. The results also showed that the conventional design method criteria to determine distances between the drain columns are very conservative. Keywords: Column drains, liquefaction, shaking table, modeling.
Column drains
Liquefaction
shaking table
Modeling
2011
10
01
209
226
https://www.ije.ir/article_71914_b325c15a6d012b938b1c9470f3233b11.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2011
24
3
Analysis of a Beam under Moving Loads
Esfandiar
Mardani
Abstract: It is assumed that a beam made of material has a physical nonlinear behavior. This beam is analyzed under the moving concentrated and distributed continuous loads. The vibration equations of motion are derived from the Hamilton's Principle and Euler–Lagrange Equation. In this study, the amplitude of vibration, circular frequency, bending moment, stress and deflection of the beam has been calculated. At the state of concentrated moving load, the obtained analytic solution has been exemplified. The results of this study indicate that when the material of the beam is considered physically nonlinear, there is no critical velocity and the resonance phenomenon doesn’t happen.
Keywords Moving load
Hamilton Principle
Euler
Lagrange Equation
Duffing Equation
Resonance
2011
10
01
227
236
https://www.ije.ir/article_71916_181bd3b5f2ecfac29f6b0b60abde1ab3.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2011
24
3
Fully Differential Current Buffers Based on a Novel Common Mode Separation Technique
Leila
Safari
seyed javad
azhari
In this paper a novel common mode separation technique for implementing fully differential current buffers is introduced. Using the proposed method two high CMRR (Common Mode Rejection Ratio) and high PSRR (Power Supply Rejection Ratio) fully differential current buffers in BIPOLAR and CMOS technologies are implemented. Simulation results by HSPICE using 0.18μm TSMC process for CMOS based structures in 1.4V supply voltage and transistor models NUHFARRY and PUHFARRY for BJT based one in 1.6V supply voltage show CMRR of 32.9dB and 33.1dB for CMOS based and BJT based fully differential current buffers respectively. The proposed fully differential current buffers show PSRR- of 114dB and 116dB in CMOS and BIPOLAR technologies respectively while their PSRR+ are 100dB and 109dB respectively. The proposed common mode separation technique can also be arranged in partial positive feedback configuration to provide high current gain too. Simulation results of this configuration in CMOS technology, show current gain and CMRR of 20.86dB and 53.91dB respectively. The proposed method tends to be a fundamental technique in current mode signal processing capable to be much further improved and utilized.
Common Mode Separation Technique
Fully Differential Current Buffer
Fully Differential Operation
High CMRR Current Input Stage
High PSRR
Low Voltage Design
2011
10
01
237
249
https://www.ije.ir/article_71917_45ea2efde9894def497843b475b161ee.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2011
24
3
Solving a bi-objective manpower scheduling problem considering the utility of objective functions
Reza
Tavakkoli-Moghaddam
Parisa
Shahnazari Shahrezaei
Hamed
Kazemipoor
This paper presents a novel bi-objective manpower scheduling problem that minimizes the penalty resulted from employees’ assignment at lower skill levels than their real skill and maximizes employees’ utility for working at a special skill level in some shifts or on some days. Employees are classified in two specialist groups and three skill levels in each specialization. In addition, the presented model executes some essential work regulations. This paper also proposes a solution procedure based on the utility of objective values. Applying this procedure, an effective point is obtained for the given problem. This is the point where both objective functions have the highest utility simultaneously.
Manpower Scheduling
Workforce Scheduling
Utility
Bi
Objective Model
2011
10
01
251
262
https://www.ije.ir/article_71920_f19dca6768b672cb657e7e244604ec97.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2011
24
3
Effect of CO2 Partial Pressure on the Thermal Decomposition Kinetics of Zinc Carbonate Hydroxide (TECHNICAL NOTE)
Amir Hossein
Nobari
Mehdi
Pishahang
Mohammad
Halali
In this work, the effect of carbon dioxide partial pressure on the calcination kinetics of high purity zinc carbonate hydroxide has been studied. Non-isothermal analysis has been performed on samples at different CO2 partial pressures by TGA and DTA. It has been found that the calcination behaviour of this material corresponds to the shrinking core model and the reaction mechanism is phase boundary controlled. The calcination reaction of zinc carbonate hydroxide starts at 240 oC. Increasing the carbon dioxide partial pressure can result in an increase in the reaction start temperature of up to 30˚C. The activation energy for the reaction is calculated as 180 ± 5 kJ/mol at significant CO2 partial pressures.
Thermal decomposition
Kinetics
Zinc carbonate hydroxide
CO2 partial pressure
2011
10
01
263
268
https://www.ije.ir/article_71922_50c55bbf3cb0784e5fa3290c3367c6df.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2011
24
3
Simulation of Premixed Combustion Flow around Circular Cylinder using Hybrid Random Vortex
Ghassem
Heidarinejad
Soodabeh
Shahriarian
This research describes the unsteady two-dimensional reacting flows around a circular cylinder. The numerical solution combines the random vortex method for incompressible two-dimensional viscous fluid flow with a Simple Line Interface Calculation (SLIC) algorithm for the propagation of flame interface. To simplify the governing equations, two fundamental assumptions namely Low Mach Number and Thin Flame Thickness are used.Numerical and graphical representation of vorticity field, velocity variation on the wake axis, the effect of combustion on stream line pattern and location of vortex element at Reynolds numbers Re=3000,9500 are presented.
Random Vortex Method
Simple Line Interface Calculation (SLIC)
Low Mach number Model
premixed combustion
Reynolds Number
2011
10
01
269
278
https://www.ije.ir/article_71923_07495105cb1e14411cedd42430768ca9.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2011
24
3
Numerical Study of Natural Convection in an Inclined Cavity with Partially Active Side Walls Filled with Cu-water Nanofluid
Mohammad hosein
Kheirkhah
Ali
Arefmanesh
Ghanbar Ali
Sheikhzadeh
Reza
Abdollahi
The buoyancy-driven fluid flow and heat transfer in a square cavity with partially active side walls filled with Cu-water nanofluid is investigated numerically. The active parts of the left and the right side-walls of the cavity are maintained at temperatures Th and Tc, respectively, with Th>Tc. The enclosure’s top and bottom walls, as well as, the inactive parts of its side walls are kept insulated. The governing equations are discretized using the finite volume method and the hybrid scheme. Using the developed code, a parametric study is undertaken and the effects of the Rayleigh number, the locations of the active parts of the side walls, the volume fraction of nanoparticles, and inclination angle of cavity on the fluid flow and heat transfer inside the cavity are investigated. It is observed from the results that the average Nusselt number increases with increasing both the Rayleigh number and the volume fraction of the nanoparticles. Moreover, the maximum average Nusselt number occurs for the middle-middle location of the thermally active parts.
Nanofluid
Natural convection
Partially Active Walls
Cavity
2011
10
01
279
292
https://www.ije.ir/article_71925_10ec92c6dd82824b6b10a74c17ba4f41.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2011
24
3
Heat Transfer on Peristaltic Transport with Slip Condition in an Asymmetric Porous Channel (TECHNICAL NOTE)
kalidas
das
Simultaneous effects of slip and heat transfer on peristaltic transport of an incompressible electrically conducting viscous fluid in an asymmetric channel is studied under the assumptions of long wavelength and low Reynold number .The asymmetry is produced by choosing the peristaltic wave train on the walls to have different amplitudes and phase.Exect solutions for stream function,velocity field, temperature profile, pressure gradient are obtained.The effects of different parameters entering into the problem on pressure rise are discussed numerically and explained graphically.Also pumping and trapping phenomena are discussed by numerical integration.
Peristalsis
slip parameter
Permeability parameter
Brinkman number
Heat Transfer Coefficient
2011
10
01
293
300
https://www.ije.ir/article_71928_bc01fd15a3e8f8fe2c9a2ab90062292e.pdf