ORIGINAL_ARTICLE
A Numerical Method for the Determination of an Effective Modules for Coated Glass Fibers Used in Phenolic Composites
It is well known that the mechanical properties of fiberglass reinforced "phenolic moulding compounds" are significantly enhanced if the glass particles are coated with silane coupling agents before compounding. It has been shown that improvements obtained by using scanning electron microscopy techniques are due to better bonding of phenolic resin to the surface of treated glass fibers. These observations prove that coated glass fibers effectively exhibit properties which are different from those of the glass itself. Thus from a modelling point of view, they can be regarded as materials having moduli different from the modulus of glass. However, considering the very small width of the coating layers used, it cannot be expected that by using direct experimental measurements of relatively large specimens, significantly different moduli for uncoated and coated glass fibers will be found. In this paper, the notion of an effective moduli for coated fibers is introduced. It is shown that such values can be numerically determined using experimentally measured bulk mechanical properties of coated glass filled composites. A trial and error procedure is developed for obtaining optimum moduli for the reinforcing phase. This scheme is based on the comparison of simulation results obtained by a previously validated finite element technique and data collected from flexural tests and fracture surface observations for different types of glass reinforced phenolic composites.
https://www.ije.ir/article_71261_d207d9343485d931111e3d66befaa7ab.pdf
2000-08-01
1
10
Glass Reinforced Composites
Silane Coupling Agents
Flexural Strength
finite element modeling
Effective Moduli
M.H.
Beheshty
hasnomail@ije.ir
1
, Iran Polymer and Petrochemical Institute
AUTHOR
V.
Nassehi
v.nassehi@lboro.ac.uk
2
Chemical & Petroleum Engineering, University Loughborough
AUTHOR
ORIGINAL_ARTICLE
Maximum Load and Minimum Volume Structural Optimization
A bi-criteria optimization is considered whose objectives are the maximization of the load sustained by a structure and the minimization of the structure's volume. As the objectives are conflicting, the solution to the problem is of the Pareto type. The problem is elaborated for a thin-walled column of cruciform cross-section, prone to flexural and torsional buckling. A numerical example is also presented.
https://www.ije.ir/article_71262_eb66145d8ff2c0e294c99e987d7819b9.pdf
2000-08-01
11
20
Bi
Criteria
optimization
Buckling
Column
Pareto Solution
Structural
J.
Pietrzak
hasnomail@ije.ir
1
, University of Beira Interior
AUTHOR
ORIGINAL_ARTICLE
Economic Analysis of Implementing Respirator Program or Ventilation System in a Manufacturing Environment
The techniques and methods of developing cost models for respirators are discussed. Models are developed and implemented in this study for nineteen types of respirators in two major classes (air-purifying and supplied-air) and one LEV system. One respirator model is selected for detailed discussion from among the twenty models. The technical cost method is used in constructing the cost models for each of the respirators and the LEV system. In this methodology, the costs of purchasing and using a typical respirator or LEV system are divided into two categories, variable costs and fixed cost s. Variable costs consist of the cost of replaceable components and probabilistic mortality cost. Fixed cost is the annualized capital requirement plus interest cost. The criteria for estimating some of the cost elements are based on existing equations in the literature, engineering judgement and manufacturer-provided information. A technical cost model results from the integration of this information into a computerized framework. The cost models for discussion are presented in the order of increasing computational complexity. Through the economic analysis, the lowest cost type in each class of respirator is determined. The determination criteria are based on the minimum total annual cost and highest benefit cost ratio. The selected lowest cost respirators are compored with the LEV system from the economic standpoint to reveal the cost optimal alternative.
https://www.ije.ir/article_71263_8f296b524df6320656c126287185d704.pdf
2000-08-01
21
32
Economic Analysis
Respirator
ventilation system
Mohammad
Saidi Mehrabad
mehrabad@iust.ac.ir
1
Industral Engineer, Iran University of science and technology
AUTHOR
ORIGINAL_ARTICLE
Direct Numerical Simulation of the Wake Flow Behind a Cylinder Using Random Vortex Method in Medium to High Reynolds Numbers
Direct numerical simulation of turbulent flow behind a cylinder, wake flow, using the random vortex method for an incompressible fluid in two dimensions is presented. In the random vortex method, the primary variable is vorticity of the flow field. After generation on the cylinder wall, it is followed in two fractional time step in a Lagrangian system of coordinates, namely convection and diffusion. No closure model is used and the instantaneous results are calculated without any a priori modeling. Regarding the Lagrangian nature of the method, there is a very good compatibility between the numerical method and physics of the flow. The numerical results are presented for a wide range of Reynolds number, 40-9500. In the initial stages, there is only an unstable symmetrical flow behind the cylinder and the vortex sheding is not started yet. But, in the high Reynolds number flows, two distinctive flow patterns, namely α and β are detected. The mechanism of generation of the primary and the secondary eddies can be related to the production, convection and diffusion of the vorticity field and the time dependent structure of the flow field in the wake zone behind the cylinder. The length of the computational domain, downstream of the cylinder, is selected 25 times of the cylinder's diameter. Regarding such a lengthy computational domain it is possible to detect the mechanism of generation, pairing and growth of the large scale structure, eddies. Although the instantaneous numerical results are calculated, no coresponding comparable results are available. Therefore, the validity of the results in this stage is only qualitative. For the quantitative comparison of the results, after the establishment of the stationary state, time averaged based indicators such as separation angle, drag coefficient, lift coefficient, Strouhal number and ... are calculated. The numerical results accurately fall within the range of the experimental measurements.
https://www.ije.ir/article_71264_87956743398f0c83b7347e0662e488fb.pdf
2000-08-01
33
50
Cylinder
Wake
Turbulent Flow
Vortex
Random Walk
Lagrangian
Drag
Lift
Separation Angle
Ghassem
Heidarinejad
gheidari@modares.ac.ir
1
Mechanical Engineering, Tarbiat Modares University
AUTHOR
S.
Delfani
hasnomail@ije.ir
2
, Tarbiat Modarres University
AUTHOR
ORIGINAL_ARTICLE
Dual Fuelling of a Direct Injection Automotive Diesel Engine by Diesel and Compressed Natural Gas
Application of Compressed Natural Gas (CNG) in diesel engines has always been important, especially in the field of automotive engineering. This is due to easy accessibility, better mixing quality and good combustion characteristics of the CNG fuel. In this study the application of CNG fuel along with diesel oil in a heavy duty direct-injection automotive diesel engine is experimentally investigated. In order to convert a diesel engine into a diesel-gas one, the so called "mixed diesel-gas" approach has been used and for this purpose a carburetted CNG fuel system has been designed and manufactured. For controlling quantity of CNG, the gas valve is linked to the diesel fuel injection system by means of a set of rods. Then, the dual-fuel system is adjusted so that, at full load conditions, the quantity of diesel fuel is reduced to 20% and 80% of its equivalent energy is substituted by CNG fuel. Also injection pressure of pilot jet is increased by 11.4%. Performance and emission tests are conducted under variation of load and speed on both diesel and diesel-gas engines. Results show that, with equal power and torque, the diesel-gas engine has the potential to improve overall engine performance and emission. For example, at rated power and speed, fuel economy increases by 5.48%, the amount of smoke decreases by 78%, amount of CO decreases by 64.3% and mean exhaust gas temperature decreases by 6.4%
https://www.ije.ir/article_71265_75894e471781bbe6fbf839f4c9a86019.pdf
2000-08-01
51
58
Dual
Fuel Engine
CNG
Automotive Diesel
A.
Mosseibi
hasnomail@ije.ir
1
, University of Tabriz
AUTHOR
V.
Pirouzpanah
pirouz@tabrizu.ac.ir
2
Mechanical Engineering, University of Tabriz
AUTHOR
ORIGINAL_ARTICLE
A Laboratory Study of Removing Arsenic from a Synthetic Copper Concentrate
Arsenic is the 20th most abundant element in the earth's crust at a level of about 2 ppm. It is a constituent of over 300 minerals and is commonly found in non-ferrous ores such as copper, lead, zinc, gold and uranium. Efficient separation of arsenic minerals from other sulphide minerals is of great importance for the metallurgical performance of flotation processes. This work was undertaken to study the separation of enargite, an arsenic-bearing mineral from chalcopyrite in copper concentrates. To achieve this aim the possible depression of enargite using some sulphide depressants was studied.
https://www.ije.ir/article_71266_cf9b4efaddf3b4952c6ef8f267e5856b.pdf
2000-08-01
59
64
ARSENIC
Sulphide Minerals
Flotation
depression
J.
Tajadod
jt400@cc.iut.ac.ir
1
, Isfahan University of Technology
AUTHOR
ORIGINAL_ARTICLE
Bioconversion and Enzymatic Activities of Neurospora Sitophila Grown Under Solid State and Submerged Fermentation on Sago Hamps (RESEARCH NOTE)
N.sitophila was grown under controlled conditions of solid state and submerged fermentation on Sago hampas. The optimum conditions of protein enrichment previously established for sugar beet pulp was used for this study. Under this condition the protein content of Sago hampas under solid state increased from 1.4 to 14.45% (W/W) whereas for Sago hampas and Sago starch, the protein content under submerged condition increased from 1.4%(W/W) and 0.7%(W/W) to 18.56%(W/W) and 43/16%(W/W) based on dry weisht of product respectively. The cellulase, a-amylase and glucoamylase activities of N.sitophila under solid state condition on Sago hampas were 9.0, 0.6 and 11.8 U/g of wet fermented solid respectively. The enzymatic activities were also measured under submerged fermentation using both Sago hampas and Sago starch as substrate.
https://www.ije.ir/article_71267_3d7ac79d00c6d47f807abe0b5f5055f2.pdf
2000-08-01
65
68
Bioconversion
Enzymatic Activities
Neurospora sitophila
Sago Hampas
C. C.
Looi
hasnomail@ije.ir
1
, University of Malaya
AUTHOR
S.A.
Shojaosadati
shoja_sa@modares.ac.ir
2
Chemical Engineering, Tarbiat Modarres University
AUTHOR
ORIGINAL_ARTICLE
A New Iterative Fuzzy-Based Method for Image Enhancement (RESEARCH NOTE)
This paper presents a new filtering approach based on fuzzy-logic which has high performance in mixed noise environments. This filter is mainly based on the idea that each pixel is not allowed to be uniformly fired by each of the fuzzy rules. In the proposed filtering algorithm, the rule membership functions are tuned iteratively in order to preserve the image edges. Several test experiments were performed in order to hlight the merit of the proposed method. The results are very promising and indicating the high performance of the proposed filter in image restoration compared with those of the filters which have been recently cited in the image processing literature.
https://www.ije.ir/article_71268_26834e49b704b03033106538a80dca95.pdf
2000-08-01
69
74
Image filtering
Fuzzy logic
image enhancement
S.A.
Motamedi
motamedi@aut.ac.ir
1
Electerical Engineering, Amirkabir University of Technology
AUTHOR
M.B.
Menhaj
menhaj@aut.ac.ir
2
Electrical Engineering, Amirkabir University of Technology
AUTHOR
F.
Farbiz
hasnomail@ije.ir
3
, Amirkabir University of Technology
AUTHOR
ORIGINAL_ARTICLE
Electrophoretic Formation of Zinc Oxide Based Ntc Rsistors (RESEARCH NOTE)
Fine zinc oxide particles were electrophoretically deposited on alumino-ferro-chrome substrates. The deposition was carried out in a cylindrical ZnO/acetone electrophoresis cell. The deposits were dried and sintered at 1030³C in air. The process resulted a porous polycrystalline ZnO cladding over the alloy core. Comb shaped silver electrodes were formed and fired at 350³C. The variation of device resistance vs. temperature was studied in air in the range of 100 - 250³C. The NTC of resistivity at 100³C and the activation energy of carrier generation was found to be 4.0% K-1 and 1.1eV respectively.
https://www.ije.ir/article_71269_28f781b438bc76f3953fcfcebe1739fb.pdf
2000-08-01
75
80
Electrophoresis
Electrophoretic deposition
Zinc oxide
Thick Film Resistors
NTC Resistors
F.
Taghibakhsh
far_ahead@yahoo.com
1
, Khaje Nasir Toosi University of Technology
AUTHOR
Faramarz
Hossein-Babaei
fhbabaei@kntu.ac.ir
2
Electerical Engineering, K. N. Toosi University of Technology
AUTHOR
ORIGINAL_ARTICLE
Static Pressure Distribution in an Excited Jet: Some Observations (RESEARCH NOTE)
A plane subsonic jet was subjected to periodic oscillations in the near nozzle region by a twin vane system. During excitation, the jet was found to spread significantly and entrain mass much more than its steady counterpart. Time averaged static pressure measured in the flow field with a disc probe exhibited prominent well defined suction regions different from that of a steady jet.
https://www.ije.ir/article_71270_b6a1cf2ca8499d9d320eaf12e3913ea2.pdf
2000-08-01
81
86
Plane Jet
Static Pressure
entrainment
Excited Jet
Mohsen
Jahanmiri
mohsenj1332@gmail.com
1
, Shiraz University of Technology, Iran
AUTHOR
ORIGINAL_ARTICLE
Signal Optimization During Radio Links Between a Transmitter and a Receiver Located in Adjacent Material Media with Differing Optical Densities (TECHNICAL NOTE)
Signal optimization is affected during radio links between a transmitter and a receiver located in adjacent material media with differing optical densities. The optimization is carried out via the automated control theory method. The radio signal obtained after the optimization is coordinated with the two media's electrical characteristics simultaneously; and this enables low power and small antenna of the transmitter, on the one hand, and low sensitivity of the receiver, on the other.
https://www.ije.ir/article_71271_b23c83ff9067d21fb94e989d607b855a.pdf
2000-08-01
87
89
Radio
signal
optimization
Optical Density
Automated Control
D. D.
Detchev
hasnomail@ije.ir
1
AUTHOR