Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
A New Generation Allocation and Expansion Planning Algorithm Including Transmission System Effects
1
15
S. H. Hosseini
H. Seifi
M. Parsa
M. R. Omidkhah
M. Farmad and M. Gaznavi
Generation Expansion Planning (GEP) is one of major modules of power system planning studies, normally performed for the nex 10-30 years horizon. The current industrial practices are to find the generation requirements based on a
nodal analysis. In this way, the allocations are not determined and subequent studies are required to find the exact locations
which as decomposed from the earlier stage, may result in non-optimum solution. A new approach is proposed in this paper in which, based on dynamic programming and sensitivity factors, GEP is performed with due to consideration of transmission
system effects. In this way, the allocations of justified generation plants are also determined. The results for Iranian Power Grid for the years 2011 to 2021 are demonstracted.
Generation Expansion Planning, Network planning, Generation allocation, Power system planning
http://jcme.iut.ac.ir/article-1-329-en.html
http://jcme.iut.ac.ir/article-1-329-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Performance Improvement of Radar Target Detection by Wavelet-based Denoising Methods
17
29
H. Saeedi
M. Modarres-Hashemi and S. Sadri
With progress in radar systems, a number of methods have been developed for signal processing and detection in radars. A number of modern radar signal processing methods use time-frequency transforms, especially the wavelet transform (WT) which is a well-known linear transform. The interference canceling is one of the most important applications of the wavelet transform. In Ad-hoc detection methods, the interference is firstly canceled and then a simple detector, like an energy detector, is
used. Therefore, we have used wavelet-based approaches to cancel the interference and then an energy detector has been employed. In this paper, it is shown that in practical cases where the performance of matched filter or near-matched filter is degraded, wavelet-based methods are more efficient. Also, we have shown that for cases where targets with slow radial velocity or one close to blind velocity are removed by the MTI filter, wavelet-based denoising has a better performance.
Radar, Detection, Energy detector, Wavelet transform, Block thresholding, Minimax thresholding
http://jcme.iut.ac.ir/article-1-330-en.html
http://jcme.iut.ac.ir/article-1-330-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
A New Heuristic Algorithm for Time-cost Trade-off Problem Taking into Account Monetary Value
31
46
Rabbani
K. Rezaie and N. Seid Foroush Lahiji
Time-cost trade-off is one of the most important subjects in project management and of interest to contractors. The goal of time-cost trade-off is sensivity analysis of project costs to changes in activity duration in order to obtain the best combination of activity duration decrease, in a way that the sum of project costs is minimized. In the heuristics presented in this area, time crashing is on the base of the minimum cost slope of activities. But since projects are usually performed over
long periods, they can be affected by interest rate. In this paper, a new heuristic algorithm is presented in order to obtain the best combination of activity duration decrease while the monetary value is taken into account, with the goal of minimizing the sum of present value of project costs
Time crashing , Time-cost trade-off, Monetary value, Rate of interest, Present Value
http://jcme.iut.ac.ir/article-1-331-en.html
http://jcme.iut.ac.ir/article-1-331-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
An Efficient Algorithm for Reducing the Duality Gap in a Special Class of the Knapsack Problem
47
57
K. Eshghi and H. Djavanshir
A special class of the knapsack problem is called the separable nonlinear knapsack problem. This problem has received considerable attention recently because of its numerous applications. Dynamic programming is one of the basic approaches for solving this problem. Unfortunately, the size of state-pace will dramatically increase and cause the dimensionality problem. In this paper, an efficient algorithm is developed to find surrogate multipliers in each stage of dynamic
programming in order to transform the original problem to a single constraint problem called surrogate problem. The upper and lower bounds obtained by solving the surrogate problem can eliminate a large number of state variables in dynamic programming and extremely reduce the duality gap according to our computational results.
Separable knapsack problem, Surrogate constraints, Dynamic programming
http://jcme.iut.ac.ir/article-1-332-en.html
http://jcme.iut.ac.ir/article-1-332-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
The Effect of Station Density and Regional Division on Spatial Distribution of Daily Rainfall
59
75
B. Saghafian
S. Rahimi Bandarabadi
H. Taheri Shahraeeni and J. Ghayoomian
Rainfall is one of the most important climatic variables in the hydrology cycle. In flood estimation as well as environmental pollution studies in medium to large watersheds not only mus temporal pattern of rainfall t be known, but also the knowledge of its spatial distribution is required. Estimation of daily rainfall distribution without comparison and selection of
suitable methods may lead to errors in input parameters of rainfall – runoff models. Interpolation methods are among the techniques for estimating spatial distribution of rainfall. In this study, Thin Plate Smoothing Splines (TPSS), Weighted Moving Average (WMA) and Kriging are applied to estimate spatial daily rainfall in the southwest of Iran. Cross validation technique is used for comparison and evaluation of the methods. The results of analysis with two different station density showed that the TPSS method with power of 2 is the most accurate method in estimating daily rainfall. Zoning of the region also increased the interpolation accuracy. Generally speaking, division of the region based on cluster analysis improves accuracy compared with division by inter basin boundaries
Cluster Analysis, Station Density, Interpolation, Geostatistics, Daily Rainfall, Cross Validation, Iran
http://jcme.iut.ac.ir/article-1-333-en.html
http://jcme.iut.ac.ir/article-1-333-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Comparision of Methods for Determining Bearing Capacity of Piles Using Standard Penetration Test (SPT) Data
77
95
A. Eslami
M. Karimpoor Fard and N. Shariatmadari
In recent years, determining bearing capacity of piles from in-situ testing data as a complement to static and dynamic analysis has been used by geotechnical engineers. In this paper, different approaches for estimating bearing capacity of piles from SPT data are studied and compared. A new method based on N value from SPT is presented. Data averaging,
failure zone and plunging failure of piles are revisited in the light of this new method. A data bank was compiled including 42 full scale pile load tests in sites where SPT was performed close to pile locations. Comparison of current methods by error investigation with statistical and cumulative probability approaches demonstrates that the new method predicts pile capacity with more accuracy and less scatter than others. Therefore, it can be applied as a suitable solution in geotechnical design.
Pile, Bearing capacity, Standard penetration test(SPT), Data filtering, Failure load
http://jcme.iut.ac.ir/article-1-334-en.html
http://jcme.iut.ac.ir/article-1-334-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Forced Hydraulic Jump by One and Two Continuous Sills in a Horizontal Stilling Basin.
97
119
M. k. Beirami and M. Ilaghi Hoseiny
Forced hydraulic jump in a horizontal stilling basin with one and two continuous sills at the downstream end of an ogee standard weir was investigated. Experiments were completed on sills of five different heights which were fixed at two different distances from the toe of the weir. The main characteristics of the jump such as the sequent depth ratio, relative roller
length, and relative energy loss were analysed. Based on the momentum equation and using an experimental coefficient, a method was adopted to predict the sequent depth ratio. Using the results of the experiments, an analytical expression was developed for the prediction of the relative roller length. These methods agree well with the writers, and other investigators, experiments. The results of experiments on one and two prolonged sills showed that by increasing the height of the sill or shortering the distance of the sill from the toe of the weir, the reduction of the sequent depth and also the roller length obtains, but the energy loss increases
Hydraulic jump, Sequent depth, Roller length, Energy loss, Stilling basin and Forced jump
http://jcme.iut.ac.ir/article-1-335-en.html
http://jcme.iut.ac.ir/article-1-335-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Behavior of Castellated I Beams Encased in Concrete
121
134
A. M. Momeni
Five methods are introduced for design of castellated I beams encased in concrete. One of the methods, plastic analysis, is thoroughly explained and the relevant equations are developed. Eight castellated I beams encased in concrete are made and tested. The theoretical design methods are all compared with the test results and the safety factor for each method is calculated. The results show that the plastic method of analysis and design is the most economical, which also gives a reasonable safety factor against beam failure
Castellated beam, Encased in concrete, Safety Factor, Beam failure, Plastic analysis
http://jcme.iut.ac.ir/article-1-336-en.html
http://jcme.iut.ac.ir/article-1-336-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Evaluation of Optimum Landfill Design by Contaminant Transport Analysis
135
153
K. Badv
Contaminant transport analysis was performed for four selected solid waste landfill designs using the computer code POLLUTE. The diffusion coefficients were determined for the natural soils (aquitard) and compacted soils from the Urumia landfill site, using the diffusion tests. These coefficients along with the geometrical, physical, and chemical parameters of the natural soil and engineered layers, as well as the dominant boundary conditions were used in the analysis of the four selected
designs for the landfill. These designs were evaluated for the contamination of the underlying aquifer in a specified period, using the drinking water standard for chloride ion. The comparisons showed that the fourth design which includes the engineered elements of a blanket type leachate collection layer and a compacted clayey liner underneath the landfill base, has more certainty in controlling the contaminant transport from the landfill base to the underlying aquifer. This type of landfill could be introduced as an optimum and semi-engineered design to be used for solid waste landfills in Iran.
Landfill, Optimum Design, Diffusion, Contaminant Transport, Aquifer
http://jcme.iut.ac.ir/article-1-337-en.html
http://jcme.iut.ac.ir/article-1-337-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
investigation of Parameters Affecting Abrasion Resistance of R.C.C.
155
176
H. M. M. Sadeghi and H. Bayat
The use of roller compacted concrete (R.C.C) without conventional cover in important hydraulic structures is investigated through laboratory observation of abrasion phenomena sujected to high velocity flow and floating particles. The main parameters affecting abrasion and erosion resistance of R.C.C. studied in the present study include: Mixed Hydraulic
Mean Radius (which collectively represents several different parameters such as shape, type of surface, fine and coarse aggregate ratio, mixture irregularity, and energy of compaction), water cement ratio, and age of R.C.C. samples. It should be noted that most references in this filed concentrate on conventional concrete abrasion with often soft surfaces. In the present
study, however, research findings on abrasion-erosion resistance of R.C.C. and their applications in new investigations will be
investigated using a new test device called Evaluation of Concrete Resistance designed by H. Bayat. The device works with
several phase flows. Single and multivariate analyses of the results, graphs, and empirical relations are used to determine abrasion and erosion resistance in terms of the above parameters. It is expected that in future only one parameter, namely, the Mixture Hydraulic Mean Radius, will suffice for evaluating R.C.C. abrasion resistance.
R.C.C.,Erosion and Abrasion Resistance, Hydraulic Mean Radius
http://jcme.iut.ac.ir/article-1-338-en.html
http://jcme.iut.ac.ir/article-1-338-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Effects of Support Conditions on Dynamic Behaviour and Seismic Response of Ghadir Bridge
177
196
S. Roushanbin
M.R. Maheri and A Rangbaran
There are a number of parameters influencing the dynamic and seismic response of bridges. Of these, two important parameters warranting special notice include: the properties of the neoperenes in the state of connection between girders and columns and the shear stiffness of underlying soil in the level of bridge substructure’s connectivity to the ground. In
this paper, the effects of these two parameters on the dynamic and seismic response of Ghadir Bridge in Isfahan are investigated. The main conclusions drawn from these investigations include: the sensitivity of the bridge’s lateral modes of vibration to the horizontal shear stiffness of the neoperenes and the substantial effects of the soil’s shear rigidity on the longitudinal modes. Based on the findings, it is recommended tha a thorough geotechnical site investigation of the soil be conducted and the properties of the underlying soil be accurately established in order to correctly identify the dynamic behaviour of a bridge.
Bridge dynamics, Bridge seismic response, Soil-structure interaction, Bridge modeling
http://jcme.iut.ac.ir/article-1-339-en.html
http://jcme.iut.ac.ir/article-1-339-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Square Joints in Railway Track Waves
197
211
S. Monajem
When rails are laid in a railway track, small gaps are left between the ends of adjoining rails to allow for the expansion of the rails when the temperature rises. Rail joints are provided to form a continuous rail path which are normally laid in standard lengths bolted together by fishplates. When two rail joints are exactly opposing each other, they are called square
(side by side) joints. Manufacturers produce rails with different standard lengths. The inner line of rails in a curve is shorter than the outer line therefore, it would be complicated to have square joints by using only rails of standard length for both inner and outer rails in the curve. If some short rails were used in the inner line, it would be possible for all joints of rails to lie opposite each other in a precise manner. It is clear that equal rail lengths can easily create square joints along the straight portion of the track. In curves with larger radii, there is a substantial difference between inner and outer arcs of the cruve. Manufacturers producing different standard lengths also produce some short rails in two or three different lengths. This paper presents a simple method of finding the location of joints in the railway curve. Previous methods (used in European and American railways) use some short rails (3 or 4 short rails) with different lengths for the inner arc. In this method, short rails of one single length are used.
Railway, Track, Wrve, Joint and Short rail
http://jcme.iut.ac.ir/article-1-340-en.html
http://jcme.iut.ac.ir/article-1-340-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Numerical and Experimental Analysis of the Effect of Flow Discharge Ratio on Flow Separation at 45 Degree Open End Water Intake
213
232
A. Keshavarzi and M. J. Kazemzadeh Parsee
Flow separation at water intake is the main cause of head loss and flow discharge reduction.
As a result, study of shape and size of separation is very essential when designing an optimum water intake. Water intake is normally built with a 90 degree angle to the main channel flow direction. However, the flow structure in this type of water intake consists of large separation size along with vortex generation. In this study, the effect of the ratio of discharge at water intake to the main channel discharge (Qr) on the location and size of separation is investigated numerically and experimentally. The velocity of the flow at each point is measured in two dimensions using electromagnetic velocity meter. The results from the experimental data indicate that the location and shape of separations are a function of flow discharge ratio (Qr). These results also indicate that at higher ratios of flow discharge, the separation occurs downstream the water intake, whereas at lower flow discharges, the flow separation occurs upstream the water intake. Additionally, the capabilites of numerical turbulence computation models including standard k-e and RNG k-e models are investigated in this study. The computed flow velocity from the turbulence models showed that the result of standard k-e model is approximately close to the experimental data when compared with RNG k-e model
45 degre intake, Flow separation, Numerical solution, Diversion structures, Water supply network
http://jcme.iut.ac.ir/article-1-341-en.html
http://jcme.iut.ac.ir/article-1-341-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
A New Implicit Dissipation Term for Solving 3D Euler Equations on Unstructured Grids by GMRES+LU-SGS Scheme
233
249
A. R. Pishevar and A. R. Shateri
Due to improvements in computational resources, interest has recently increased in using implicit scheme for solving flow equations on 3D unstructured grids. However, most of the implicit schemes produce greater numerical diffusion error than their corresponding explicit schemes. This stems from the fact that in linearizing implicit fluxes, it is conventional to replace the Jacobian matrix in the dissipation term by its constant spectral radius. The objective of the present
study is to develop a modified implicit solver based on Roe scheme so that its numerical dissipation is as much as the explicit one. In the proposed scheme, the Krylov subspace method with a LU decomposition preconditioner (GMRES+LU-SGS) is used to solve the linear systems. The efficiency of this method is shown by presenting some examples at the end.
Euler equation, Unstructured 3D grid, numerical diffusion, GMRES+LU-SGS
http://jcme.iut.ac.ir/article-1-342-en.html
http://jcme.iut.ac.ir/article-1-342-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Hydrodynamic Resistance Reduction in Catamaran Assisted Hydrofoils
251
269
M. Asgaree and M. S. Seif M.
The present paper contains the test results of a planing catamaran model. The aim of the tests was to study the effect of hydrofoil in these types of crafts. First, experiments were carried out on the bare body (i.e. without hydrofoils) to obtain non-dimensional hydrodynamic resistance coefficient versus speed. Then, the model with hydrofoils, by various locations and attack angles were subjected to tests and the results were compared with those from the tests with the bare body. Results show that
great reduction in hydrodynamic resistance of hydrofoil-supported catamaran is accessible especially at high speeds. In addition, hydrofoils positioning is important and un-suitable designs may result in instability in motion and increased in hydrodynamic resistance.
Catamaran Vessel, Hydrofoil, Model test, Hydrodynamic Resistance
http://jcme.iut.ac.ir/article-1-343-en.html
http://jcme.iut.ac.ir/article-1-343-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Stability Analysis for Wake Flow Behind a Flat Plate
271
282
M. Kahrom
K. Alavie and M. M. Jafariean
Neutral stability limits for wake flow behind a flat plate is studied using spectral method. First, Orr-Sommerfeld equation was changed to matrix form, covering the whole domain of solution. Next, each term of matrix was expanded using Chebyshev expansion series, a series very much equivalent to the Fourier cosine series. A group of functions and conditions are applied to start and end points in the mathematical domain of the solution so as to avoid error accomulation at these points. The scheme ends with two matrices which result from the Orr-Sommerfeld equation. These matrices are solved, in conjunction,
with boundary conditions ending up with a curve of neutral points of stability for an assumed velocity profile. Results are compared with other existing numerical methods and experiments, and the accuracy of the method is confirmed.
Orr-Sommerfeld, Disturbance, Neutral Stability, Spectral Method, Chebeyshev Series, Shear flow
http://jcme.iut.ac.ir/article-1-344-en.html
http://jcme.iut.ac.ir/article-1-344-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Investigations on Cold Rolling of Strip in Attendance of Hydrodynamic Lubrication
283
297
M. Salimi and S. Asghari
In this paper an analytical model for cold rolling of strip has been described. This model is developed based on the slab method of analysis and the hydrodynamic lubrication. The characteristics of rolling are obtained from the equations of equilibrium and the plate was allowed to strain harden assuming that the lubricant behaves as a Newtonian fluid. The shear stress to the plate is obtained by calculating the thickness of the lubricant film by employing a viscosity-pressure-temperature relation. The governing equations are obtained by composing these relations and the final differential equations have been solved. From the solution of the final equation, the rolling force، torque and shear stress to the plate are calculated. To verify the validity of
the proposed model, these values are compared with experimental and analytical results of other investigators. It was also noted that by employing the proposed analytical model, a large amount of computation time and costs are saved
Cold rolling of strip, Hydrodynamic lubrication, Slab method, Newtonian lubricant
http://jcme.iut.ac.ir/article-1-345-en.html
http://jcme.iut.ac.ir/article-1-345-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Temperature Distribution of a Non gray Gas between Two Parallel Planes Using Exponential Wide Band Model
299
314
R. Hosseini
M. Vaziri
and M. Bidi
In this paper, the Radiation Transfer Equation(RTE) for a non-gray gas between two large parallel planes has been
solved and the temperature distribution obtained. With the RTE, solution heat fluxes are also determined. Since and are two components of most combustion products, the problem has been solved for these two gases. The results were, whenever possible, compared with data reported elsewhere. Since the simulation of exact absorbing bands has been used, it can be claimed to be relatively close to exact solution. From the results otained, it can be maintained that treating, the above mentioned gases as a gray gas could cause considerable errors in the determination of temperature distribution and heat fluxes. The error would be more for water vapour than for carbon dioxide.
Gas radiation, Non-gray gas, Carbon dioxide, RTE, Temperature distribution, Gas absorbtivity and emissivity
http://jcme.iut.ac.ir/article-1-346-en.html
http://jcme.iut.ac.ir/article-1-346-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Heat Transfer from a Tube Bank in Cross Flow in a Duct
315
325
Nouri and A. M. Lavasani
An experimental investigation on heat transfer coefficient is presented from three horizontal tubes in a vertical array in a duct for 500<ReD<6000. A mass transfer measuring technique based on psychrometry chart is used to determine heat transfer coefficient. The diameter of the tubes is 11 mm each spaced 40 mm apart and in-line pitch ratio varies
in the range 0.055<D/W<0.22. The experimental results show that the Nusselt number of each tube increases by increasing D/W. Also the increase of the second tube Nusselt number is more than that of the third one.
Experimental method, Heat and Mass transfer, Tube bank, Duct
http://jcme.iut.ac.ir/article-1-347-en.html
http://jcme.iut.ac.ir/article-1-347-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Microstructural Effect on the Weldability of 25Cr-35Ni Cast Steel
327
336
M. Shamanian and A. Saidi
The 25Cr-35Ni heat resistant steel has been widely used when resistance to oxidation and creep rapture at elevated temperatures is required. In this paper, the microstructural effect on the weldability of this alloy is investigated. The results of this study indicate that this steel has a perfect weldability in the as cast condition but does not possess good weldability in the aged condition. The as cast microstructure of 25Cr-35Ni steel consists of austenite matrix and a network of primary carbides, while the aged condition consists of austenite matrix and y primary and secondary carbides. The morphological change of primary
carbides and the secondary carbides precipitate formation, reducing the elongation and ductility of aged steel, should have enhanced the steel susceptibility to cracking, particularly in the area of the eutectic carbides, and hence, the reduced weldability of the steel. The cracking observed was of the intergranular type and spread along the eutectic carbides. It was found that the carbides in the as cast steel consisted of NbC and M23C6, whereas that of the aged steel also exhibited Ni16Nb6Si7 and M23C6 carbides
25Cr-35Ni cast steel, Weldability, Microstructure, As cast, Aged
http://jcme.iut.ac.ir/article-1-348-en.html
http://jcme.iut.ac.ir/article-1-348-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Optimization of Reductive Leaching of Tidar Cobalt Ore Using Taguchi Method
337
354
M. M. Diband Khosravi and M. Abdollahiy
Reductive leaching was used to dissolve metals, especially cobalt, present in Fars Tidar mine,. In this paper, cobalt ore was leached with sulphuric acid in the presence of phenol to determine the effects of various factors on leaching. These factors included temperature, acid concentration, time, phenol content, pulp density, and interaction between some of the parameters. The results indicated that temperature was more effective on SN ratio (Signal to Noise ratio) which was found to be about 80%. The effecst of time and acid concentration on SN ratio were also determined at about 8% and 4 %, respectively. Although the effect of phenol content on cobalt leaching was too low but dissolution of cobalt decreased in the absence of phenol. Therefore, it was concluded that phenol was one of the factors in effective the leaching process. Anyway, three parameters
including temperature, acid concentration, and time were selected as more effective parameters. Consequently optimum conditions can be obtained with high levels content of temperature, acid concentration, and time with low levels of phenol and pulp density.
Reductive leaching, Cobalt, Sulphuric acid, Optimization, Taguchi method, Tidar mine, SN ratio, Phenol
http://jcme.iut.ac.ir/article-1-349-en.html
http://jcme.iut.ac.ir/article-1-349-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Hot Mercerizing of Cotton/Polyester Blend Fabric Effect of Alkali Treatment Temperature on Ttensile Properties , Weight Loss and Shrinkage of Fabric
355
365
S. M. Mortazavi and M. Sedighipoor
The presence of defects in cold mercerizing of cotton goods led to the creation of a new method, called hot mercerizing in which caustic soda solution is used at a high temperature. Hot mercerizing is successfully used in cotton blended with some other fibers. In cotton/polyester blend fabrics, this treatment serves a dual purpose: subjectively, it imparts a silklike
soft handle to the polyester and brings about mercerizing of the cotton. In this work, the mercerizing operation with caustic soda solution was performed on a 65/35 polyester/cotton fabric in sixteen different temperatures (from 15°C to 90°C), in two states: with tension and without tension. Finally, the effect of temperature of treatment on some properties of fabric such as tensile properties, weight loss, and shrinkage have been studied. Alkali treatment cause weight loss in cotton/polyester blend fabrics, the main part of the weight loss attributed to the polyester component of the blend. Increasing temperature leads to a corresponding increased in weight loss. The resulting weight loss leads to more yarn release and consequently, to the improvement of the drape and soft handle in the fabric. However, it decreases the tensile strength and causes weakness of the fabric, therefore, an optimum of temperature must be considered. In the alkali treatment, the internal stresses in the fabric can be released. Release of tension in the fabric causes shrinkage, particularly in the warp direction. The effect of tension on properties of cotton/polyester blend fabric is not considerable in alkali treatment.
Hot mercerizing, Cotton/Polyester blend fabric, Alkali treatment, Caustic soda solution, Weight loss, Handle, tensile properties, Shrinkage
http://jcme.iut.ac.ir/article-1-350-en.html
http://jcme.iut.ac.ir/article-1-350-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Effects of Changes in Front Drafting Rollers Geometry on the Properties of Ring Spun Yarns
367
380
A. A. Gharehaghaji and M. Rafimanzelat
Regarding the importance of ring spinning method among spinning systems, great potentials exist for research about on the improvement of the quality and properties of ring spun yarn. This study aims to improve yarn quality by changing the shape and dimensions of spinning triangle through forming a groove in the middle zone of the front darfting
roller with a curvature of 5 to 7 mm. For the top drafting roller, we used an elastic O-Ring with dimensions similar to those of the groove. With this change, the geometry of spinning triangle is expected to change as an Euclidean geometry to a half cone Riemannian shape. The results show improvement in yarn tenacity, elongation at break, yarn evenness and faults, shape of spinning baloon, decrease in yarn tension and yarn breakage, improvement in fiber packing in the yarn cross section, more evenness in the yarn count and twist, and, finally, better inter-structure compared to the normal ring spun yarn.
Ring spinning، Spinning triangle، Yarn tenacity، Yarn tension، Fiber spinning-in coefficient، Yarn in terstructure
http://jcme.iut.ac.ir/article-1-351-en.html
http://jcme.iut.ac.ir/article-1-351-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Analysing of Continuous Welded Turnouts
381
390
J. A. Zakeri and F. J. Jie
Continuous welded turnouts are important for CWR track through the railway station. According to equivalent resistance and non-linear theories and the principle of force diagram, a new method of theoretical calculation for continuous welded turnouts was developed. The continuous welded turnouts designed and installed according to the new theory behaved fairly well. The data collected on sites basically agreed with those of theoretical calculation. It was proved that the calculation theory is correct and values of calculation parameters are reasonable.
Calculation theory of turnouts, Continuous welded turnout
http://jcme.iut.ac.ir/article-1-352-en.html
http://jcme.iut.ac.ir/article-1-352-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Analysis of Thin-Walled Steel Sections Filled with Concrete Using Non-Linear Finite Element Method
391
399
J. Emadi
Being economical and performing well under cyclic loads, steel sections filled with concrete have been widely used in structural buildings. Extensive studies and experiments have been conducted to investigate the influence of different parameters and loadings on the behavior of these structural components. Based on the data available from previous experiments and studies, this paper discusses the behavior of composite columns. The results of 3D-non-linear finite element analysis of thin-walled steel sections filled with concrete are presented. Lastly, comparisons are made between results from finite element analysis and experimental data available about the specimens. Using a trial and error method, the finite element model was calibrated and was used to evaluate the capacity of specimens that were not tested in the laboratory. The capacities of the sections were calculated
based on the LRFD design method. The results are compared to evaluate the accuracy of the proposed method. Because of the increase in the use of high strength materials in structures, the effects of increase in concrete and steel strengths on the behavior of composite columns are discussed in this paper. Also the effects that the change in the thickness of the steel shell may have on the behavior of composite columns are argued.
Composite columns, Box cross-sectioned columns, Non-linear finite element
http://jcme.iut.ac.ir/article-1-353-en.html
http://jcme.iut.ac.ir/article-1-353-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Effect of Limestone Powder on Compressive Strength of Concrete Containing Silica Fume and Optimization of Mix Design Using Response Surface Method
401
411
D. Mostofinejad and M. Reisi
Silica fume has been largely used in concrete in recent decades due to its effect on improvement of strength and
durability of concrete. On the other hand, attention has been recently paid to the use of limestone powder as a substitute for part of cement in concrete, basically because of its low price and its positive effect on the durability of concrete. The aim of the current study is the investigation of the interactive effect of silica fume and limestone powder on the compressive strength of concrete and the optimization of the mix design. To do so, 27 mix designs including 3 water-to-cementitious materials ratios (W/CM=0.25, 0.3 and 0.4) 3 silica fume-to-cementitious materials ratios (SF/CM=%0, %5 and %10) and 3 limestone powder-to-cement ratios (LP/C=%0, %15 and %30) were used and 28-day compressive strength of the cubic concrete specimens were determined. Then, the interactive effect of silica fume and limestone powder on compressive strength of concrete was investigated using isoresponse curves. Furthermore, the optimization of the mix design for concretes containing silica fume and limestone powder was carried out using “cost effective factor” (CEF) which is defined compressive strength divided by cost of concrete.
Concrete, Limestone powder, Silica fume, Compressive strength, Response surface method.
http://jcme.iut.ac.ir/article-1-354-en.html
http://jcme.iut.ac.ir/article-1-354-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Thermo-economic Analysis of Power Cycles
413
424
A. R. Azimian
Exergy analysis is based on combined first and second laws of thermodynamics and is a useful tool to analyze the energy systems in a better and more realistic way than an energy analysis, based on the first law of thermodynamics. Combination of exergy from thermodynamics with conventional concepts from engineering economy which is referred to as thermo-economy (exergo-economy) is a valuable tool to analyze the energy systems in a better way. In this paper, efforts are made to
apply the concept of thermo-economy to analyze two power cycles (a combined Gas and Steam cycle and a conventional steam power plant). In this analysis, the results of an exergy calculation are combined with the economic aspects such as investment costs, fuel costs, and also operation and maintenance costs. The goal of this study is to show how to implement the concept of thermo-economy to these cycles and also how to estimate the price of the product (electric power generated). Assessment of the components exergy destruction costs is a second objective in this study. Results obtained from this analysis clearly show the effect of the cost breakdown and the component performance on the price of the final product. Comparison of the price of the product in these cycles shows that the combined cycle is superior to the conventional steam power plant.
Exergy analysis, Thermo-economy, Combined cycle, Steam power plant, Component efficiency
http://jcme.iut.ac.ir/article-1-355-en.html
http://jcme.iut.ac.ir/article-1-355-en.pdf
Isfahan University of Thechnology
Computational Methods in Engineering
2228-7698
2423-5741
24
1
2005
7
1
Effects of Coating Golegohar-Chadormalu Pellet on Its Behaviour in Direct Reduction Process
425
433
J. Safarian-Dastjerdi and A. Saidi
A higher bustle temperature in midrex direct reduction process is always desirable due to its positive effect on the productivity and DRI quality. The limit of the bustle temperature is related to the sticking or clustering behaviour of oxide pellets during the reduction in the reactor. It has been well estabilished that coating of oxide pellets by a refractory material decreases its
tendency to clustering. In this study, the clustering behaviour of oxide pellets (produced from Golegohar-Chadormalu iron ore) during redution at different temperatures was investigated. The effect of coating with different amounts of hydrated lime on the clustering behaviour was also examined. Microscopic examination of coated pellets shows a porous, non-continious layer of Ca(OH)2 being fromed on the surface of the pellets. The clustering tendency of coated pellets, measured by the standard sticking test at pilot scale, was much lower, compared with normal (uncoated) pellets, while their reducibility was the same.
Sponge iron, Direct reduction, Coated pellet, Clustering of DRI
http://jcme.iut.ac.ir/article-1-356-en.html
http://jcme.iut.ac.ir/article-1-356-en.pdf