Ahmad Saghafi; Seyyed Mehdi Fakhraee; Manoochehr Manteghi
Abstract
Ultra-wideband (UWB) radio is a promising technology for low-cost, high-rate communications at short ranges. However, high bandwidth and low power of the UWB signals impose some difficult challenges in signal processing and implementation of the receiver. Acquisition of the signal timing is the first ...
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Ultra-wideband (UWB) radio is a promising technology for low-cost, high-rate communications at short ranges. However, high bandwidth and low power of the UWB signals impose some difficult challenges in signal processing and implementation of the receiver. Acquisition of the signal timing is the first task to be performed in a coherent receiver. The high bandwidth of UWB signals demand for fine time resolution search of the uncertainty region. Thus, for an accurate acquisition, the uncertainty region must be searched in small step sizes, imposing a large search space. Moreover, the low transmission power of UWB systems requires the receiver to observe the received signal for a long time in order to make a reliable decision. These are the two reasons that cause the receiver to spend a long time for acquisition of the signal timing. The fine time resolution, on the other hand, results in a large number of resolvable multipath components which locking to many of them might be treated as a good estimate of the timing information of the received signal. Hence, in a multipath channel there may be more than one phase that could be considered a reliable estimate of the true signal timing.
In this paper, we propose a new two-stage search space reduction technique which speeds up the acquisition process without adding additional complexity to the conventional serial acquisition method. Specifically, we divide the search space into some groups of consecutive phases and the first stage tries to find a set of possible positions of the true phase relative to the positions of the groups using a special template signal. When a set of phases?one from each group?is declared to include the true phase, the second stage tries to find the absolute position of the true phase by searching the relative positions in each group using a simple template signal. The performance of the proposed method is analytically evaluated in terms of mean acquisition time and the results are validated through computer simulations. For the simulations we performed in this paper, a complete fully parameterized model of the system is designed using MATLAB/Simulink software. The results show a significant improvement in acquisition time with no additional complexity.
Hassan Monsef; Taher Ghomian
Abstract
This paper introduces Artificial Neural Network (ANN) method for measuring voltage in the Optical Voltage Transducer (OVT) using one or more electric field sensors. In order to obtain an accurate voltage measurement with minimum number of sensors, first the locations of sensors are specified by quadrature ...
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This paper introduces Artificial Neural Network (ANN) method for measuring voltage in the Optical Voltage Transducer (OVT) using one or more electric field sensors. In order to obtain an accurate voltage measurement with minimum number of sensors, first the locations of sensors are specified by quadrature method. Then the electric field intensity at these locations is provided to ANN for the calculation of applied voltages. Less number of sensors with no displacement required to obtain high accuracy is the most important advantage of this method. The numerical simulations demonstrate the effectiveness of this technique.
Masoud Riazi; Mohammad Reza Esfahani
Abstract
In this research, using the Modified Compression Field Theory (MCFT), a new truss based model is proposed to predict the behavior of reinforced concrete coupling beams with diagonal reinforcement. The model is able to consider the effects of shear and axial forces and bending moment, simultaneously. ...
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In this research, using the Modified Compression Field Theory (MCFT), a new truss based model is proposed to predict the behavior of reinforced concrete coupling beams with diagonal reinforcement. The model is able to consider the effects of shear and axial forces and bending moment, simultaneously. The proposed model includes a nonlinear shear spring, an axial spring, two inclined truss members and some nonlinear springs for considering bending deformations. The results of the proposed model were compared with several test results conducted by the authors and other researchers. The comparison shows that the proposed model can predict shear behavior of coupling beams, appropriately.
Ali Asghar Mirghasemi; Helia Rahmani
Abstract
In some natural events such as soil failure the deformations are localized in narrow restrictions, which are called shear bands. This event which is a fundamental phenomenon in granular material, has been widely investigated during recent decades within expensive experimental tests and also some numerical ...
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In some natural events such as soil failure the deformations are localized in narrow restrictions, which are called shear bands. This event which is a fundamental phenomenon in granular material, has been widely investigated during recent decades within expensive experimental tests and also some numerical simulations. Most of previously used numerical methods are based on continuum theories describing shear bands as interfaces along which solid masses move like rigid blocks. In this interpretation many physical events such as changes of the soil structure around failure line are neglected. In this paper the discrete element method is used to simulate the shear bands. Since in this method some of the problems of experiments and simulations are solved,
It would be an ideal method to obtain the stresses and strains, and also to investigate the behavior of shear bands in a granular media, while exposing to external forces. In this research by the use of DEM and conducting series of biaxial tests on assemblies of two-dimensional ellipse shaped particles, the effect of different factors such as average grain size, particle shape and confining pressure on the shear bands are studied and the results show that some investigated factors like average grain size and confining pressure have considerable effect on the shear bands characteristics.
The main results can be summarized as follows:
• The amount of rotation is a very sensitive characteristic and it changes considerably by all of the factors measured in this research.
• The most affecting factors on the displacement of the particles across the shear bands are the loading rate and confining pressure. Moreover by increasing the particle size the displacements increase with a great amount but if these values are divided by the particle radius, no significant changes in the particle displacement will be observed. Other factors do not seem to have any effects on this issue.
• 6-13d50 seems to be the best estimation for the shear band thickness, and other controlled factors affect this value within this restriction. The width of the shear bands seems to increase by the loading rate and confining pressure increase.
• The inclination of this localization is mostly affected by confining pressure (which increase leads to angle decrease), porosity (which increase leads to angle decrease), grading (its uniformity causes smaller shear band angles), and size (greater sizes of grains would result in failure with lower angles of sear band). Among these factors grain size has the least effect.
Ahmad Darabi; Hamid Lesani; Teymour Ghanbari Hashemabadi
Seyyed Mohammad Taghi Fatemi Ghomi; Seyyed Ali Lesani; Ahmad Kouchak Zadeh
Abstract
Neural networks because of their abilities are used to patterns recognition. In statistical process control charts, a common cause variation distort expected form of unnatural patterns and so detection of assignable causes efficiently and precisely in a real-time is difficult. Therefore it would be logical ...
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Neural networks because of their abilities are used to patterns recognition. In statistical process control charts, a common cause variation distort expected form of unnatural patterns and so detection of assignable causes efficiently and precisely in a real-time is difficult. Therefore it would be logical to propose models based neural networks for recognition and analysis of patterns in process control charts. Nearly most of investigations of the application of neural networks to control chart patterns recognition solely have emphasized the detection of patterns and have not considered analysis and extraction detailed information which is important for effectively determining the assignable causes. Moreover, some of the patterns generator functions do not represent completely the real world situation. This paper proposes a model for discrimination and analysis of basic and concurrent patterns. This model first recognizes unnatural patterns. Then it estimates their starting point and finally determines the values of corresponding parameters. In design of proposed model, the development of areas of application has been emphasized. Numerical results indicate that the components of proposed model have suitable and effective performance
Hiva Roboubi; Yadollah Mortazavi; Abbas Ali Khodadadi
Abstract
For the first time, this research reports the formation of nanoporous layers of metals on the surface of metal substrates by Raney method and their conversion to corresponding porous perovskite layers. The noble metals doped perovskites are used as catalytic converter for reducing automotive pollutants. ...
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For the first time, this research reports the formation of nanoporous layers of metals on the surface of metal substrates by Raney method and their conversion to corresponding porous perovskite layers. The noble metals doped perovskites are used as catalytic converter for reducing automotive pollutants. The use of perovskite as a substrate for the noble metals can reduce the need for such metals by as much as 70%. The metal surface is treated by plastic deformation at high pressures or quenching to create microstructures, and then an aluminum-metal alloy layer is formed on the surface of the metal by its hot dip aluminizing at 750oC. At the same temperature, the aluminum is diffused into the metal surface layer as deep as 30nm for 1h. Subsequently the sample is gradually quenched or cooled and the aluminum is extracted by soda solution. Nanostructures of about 30 nm are obtained by combined Raney method together with the plastic deformation process. Quenching of the alloy creates even smaller nanostructures. The porous metal layer is impregnated with lanthanum nitrate for one or more times and calcined at 900oC to create the porous perovskite layer on the surface of the metal substrate as monolith. The perovskite completely converts CO and C2H6 (as representative of the exhaust unburned hydrocarbons).
Mansour Haji Hosseinlou; Arash Abbasi
Abstract
Roundabout is one of the most effective intersection control methods in the world. Although, they have often been used in Iran, but, the methods which are proposed to analyze roundabouts are very old and new regulations are not implemented for analyzing modern roundabouts. There are strong needs to apply ...
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Roundabout is one of the most effective intersection control methods in the world. Although, they have often been used in Iran, but, the methods which are proposed to analyze roundabouts are very old and new regulations are not implemented for analyzing modern roundabouts. There are strong needs to apply new modern analyzing methods for studying roundabouts in Iran. Also, these methods should be compared with other methods for controlling intersections. The results from previous studies show that roundabouts perform better than the intersection with two-way stop and all-way stop control in various cases. The most important aim of this research is to compare the capacity and delay of roundabout with signalized intersection at the same conditions. In this paper, the methods which are applied in the developed countries for calculating the capacity and delay of roundabout are considered and the most effective and suitable one is chosen for using in Iran. The method of Australia was selected and proposed for analyzing roundabouts. For analyzing the capacity and the delay of signalized intersection the HiCAP software was used. This software works based on HCM2000 theoretical model. Two signalized intersection of Isfahan city were selected for the case study. The roundabout plan was used in the same situations with the same space and traffic data. The diagram of entrance delay and capacity of roundabout and signalized intersection was obtained and analyzed. One of the main results of this analysis is that a two-lane roundabout in same space intersection with inscribed circle diameter of 55 to 60 meter can pass about 3400 vehicles per hour with lower delay comparing to intersection. Another result is preference of roundabouts in low and medium volumes comparing to intersections. In such volumes roundabouts have very low delays comparing to intersections. As an important point, this research shows capability of the selected method for analyzing roundabout and represents formula calibration with regard to Iran conditions.
S. ALAGU; R. KALA
Abstract
The notion of Asteroidal triples was introduced by Lekkerkerker and Boland [6]. D.G.Corneil and others [2], Ekkehard Kohler [3] further investigated asteroidal triples. Walter generalized the concept of asteroidal triples to asteroidal sets [8]. Further study was carried out by Haiko Muller [4]. In this ...
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The notion of Asteroidal triples was introduced by Lekkerkerker and Boland [6]. D.G.Corneil and others [2], Ekkehard Kohler [3] further investigated asteroidal triples. Walter generalized the concept of asteroidal triples to asteroidal sets [8]. Further study was carried out by Haiko Muller [4]. In this paper we find asteroidal numbers for Direct product of cycles, Direct product of path and cycle, Strong product of paths and cycles and some more graphs.
Mehrdad Raisee Dehkordi; Arman Rokhzadi
Abstract
Roughness elements or turbulence promoters have been widely used to enhance heat transfer in cooling passages of modern gas turbine blades. Although such ribs substantially enhance heat transfer, the heat transfer coefficient is reduced immediately at corner downstream of each rib, creating hot spots. ...
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Roughness elements or turbulence promoters have been widely used to enhance heat transfer in cooling passages of modern gas turbine blades. Although such ribs substantially enhance heat transfer, the heat transfer coefficient is reduced immediately at corner downstream of each rib, creating hot spots. To remove such hot spots some of the ribs can be detached from the channel walls. In this paper, this idea is investigated using numerical methods. In this study, turbulent flow and heat transfer through three types of channels, namely: 1) a channel with detached ribs from a wall 2) a channel with detached ribs from both walls and 3) a channel with alternative attached-detached ribs on both walls have been investigated. Computations presented in this research have been obtained with the linear and non-linear k-? models. The numerical method in this work is finite volume methodology and simple algorithm. The governing equations are discretized in a semi-staggered grid system. In all equations the convective terms are approximated using Hybrid scheme. The numerical results for the channel with detached ribs close to one principal wall showed that both the linear and non-linear k-? models are able to predict the length and width of the wake downstream of the detached ribs, although both models produce weaker wakes compared with experimental data. Both models "specially the non-linear k-? model" predict lower stream-wise velocity and turbulent intensities closed to the ribbed wall. As a result, both turbulence models "and specially the non-linear k-? model" substantially under-predict the wall heat transfer. For the channel with ribs detached close to both walls, both turbulence models produce better heat transfer predictions though still predict lower heat transfer levels. Finally, for the channel with alternative attached-detached ribs, both turbulence models fail to predict reliable heat transfer levels in first half of the channel but return acceptable Nusselt levels in the second half of the channel.
R. Ponraj; K. Annathurai; R. Kala
Abstract
In this paper we generalize the remainder cordial labeling, called $k$-remainder cordial labeling and investigate the $4$-remainder cordial labeling behavior of certain graphs.
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In this paper we generalize the remainder cordial labeling, called $k$-remainder cordial labeling and investigate the $4$-remainder cordial labeling behavior of certain graphs.
M. E. Abdel-Aal; S. Minion; C. Barrientos; D. Williams
Abstract
Mean labelings are a type of additive vertex labeling. This labeling assigns non-negative integers to the vertices of a graph in such a way that all edge-weights are different, where the weight of an edge is defined as the mean of the end-vertex labels rounded up to the nearest integer. In this paper ...
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Mean labelings are a type of additive vertex labeling. This labeling assigns non-negative integers to the vertices of a graph in such a way that all edge-weights are different, where the weight of an edge is defined as the mean of the end-vertex labels rounded up to the nearest integer. In this paper we focus on mean labelings of some graphs that are the result of the corona operation. In particular we prove the existence of mean labelings for graphs of the form G ⊙ mK1 in the cases where G is an even cycle or G is an α-mean graph of odd size and the cardinalities of its stable sets differ by at most one unit. Under these conditions, we prove that G ⊙ P2 and G ⊙ P3 are also mean graphs, and that the class of α-graphs is equivalent to the class of α-mean graphs.
Mahdi Imanparast; Seyed Naser Hashemi; Ali Mohades
Abstract
We study the problem of computing the diameter of a set of $n$ points in $d$-dimensional Euclidean space for a fixed dimension $d$, and propose a new $(1+\varepsilon)$-approximation algorithm with $O(n+ 1/\varepsilon^{d-1})$ time and $O(n)$ space, where $0 < \varepsilon\leqslant 1$. We also ...
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We study the problem of computing the diameter of a set of $n$ points in $d$-dimensional Euclidean space for a fixed dimension $d$, and propose a new $(1+\varepsilon)$-approximation algorithm with $O(n+ 1/\varepsilon^{d-1})$ time and $O(n)$ space, where $0 < \varepsilon\leqslant 1$. We also show that the proposed algorithm can be modified to a $(1+O(\varepsilon))$-approximation algorithm with $O(n+ 1/\varepsilon^{\frac{2d}{3}-\frac{1}{2}})$ running time. Our proposed algorithms are different with the previous algorithms in terms of computational technique and data structures. These results provide some improvements in comparison with existing algorithms in terms of simplicity and data structure.
A. Ghodousian; Tarane Azarnejad; Farnood Samie Yousefi
Abstract
Minimum and maximum operators are two well-known t-norm and s-norm used frequently in fuzzy systems. In this paper, two different types of fuzzy inequalities are simultaneously studied where the convex combination of minimum and maximum operators is applied as the fuzzy relational composition. ...
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Minimum and maximum operators are two well-known t-norm and s-norm used frequently in fuzzy systems. In this paper, two different types of fuzzy inequalities are simultaneously studied where the convex combination of minimum and maximum operators is applied as the fuzzy relational composition. Some basic properties and theoretical aspects of the problem are derived and four necessary and sufficient conditions are presented. Moreover, an algorithm is proposed to solve the problem and an example is described to illustrate the algorithm.
A. Ghodousian; M. Jafarpour
Abstract
In this paper, optimization of a linear objective function with fuzzy relational inequality constraints is investigated where the feasible region is formed as the intersection of two inequality fuzzy systems and Dombi family of t-norms is considered as fuzzy composition. Dombi family of t-norms includes ...
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In this paper, optimization of a linear objective function with fuzzy relational inequality constraints is investigated where the feasible region is formed as the intersection of two inequality fuzzy systems and Dombi family of t-norms is considered as fuzzy composition. Dombi family of t-norms includes a parametric family of continuous strict t-norms, whose members are increasing functions of the parameter. This family of t-norms covers the whole spectrum of t-norms when the parameter is changed from zero to infinity. The resolution of the feasible region of the problem is firstly investigated when it is defined with max-Dombi composition. Based on some theoretical results, a necessary and sufficient condition and three other necessary conditions are derived for determining the feasibility. Moreover, in order to simplify the problem, some procedures are presented. It is shown that a lower bound is always attainable for the optimal objective value. Also, it is proved that the optimal solution of the problem is always resulted from the unique maximum solution and a minimal solution of the feasible region. A method is proposed to generate random feasible max-Dombi fuzzy relational inequalities and an algorithm is presented to solve the problem. Finally, an example is described to illustrate these algorithms.
Stephen J. Gismondi
Abstract
A compact formulation of the set of tours neither in a graph nor its complement is presented and illustrates a general methodology proposed for constructing polyhedral models of decision problems based upon permutations, projection and lifting techniques. Directed Hamilton tours on n vertex graphs are ...
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A compact formulation of the set of tours neither in a graph nor its complement is presented and illustrates a general methodology proposed for constructing polyhedral models of decision problems based upon permutations, projection and lifting techniques. Directed Hamilton tours on n vertex graphs are interpreted as (n-1)- permutations. Sets of extrema of Birkhoff polyhedra are mapped to tours neither in a graph nor its complement and these sets are embedded into disjoint orthogonal spaces as the solution set of a compact formulation. An orthogonal projection of its solution set into the subspace spanned by the Birkhoff polytope is the convex hull of all tours neither in a graph nor its complement. It’s suggested that these techniques might be adaptable for application to linear programming models of network and path problems.
R. Ponraj; Rajpal Singh; S. Sathish Narayanan; A. M. S. Ramasamy
Abstract
Let G be a (p, q) graph. Let f : V (G) → {1, 2, . . . , k} be a map. For each edge uv, assign the label gcd (f(u), f(v)). f is called k-prime cordial labeling of G if |vf (i) − vf (j)| ≤ 1, i, j ∈ {1, 2, . . . , k} and |ef (0) − ef (1)| ≤ 1 where vf (x) denotes the number ...
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Let G be a (p, q) graph. Let f : V (G) → {1, 2, . . . , k} be a map. For each edge uv, assign the label gcd (f(u), f(v)). f is called k-prime cordial labeling of G if |vf (i) − vf (j)| ≤ 1, i, j ∈ {1, 2, . . . , k} and |ef (0) − ef (1)| ≤ 1 where vf (x) denotes the number of vertices labeled with x, ef (1) and ef (0) respectively denote the number of edges labeled with 1 and not labeled with 1. A graph with a k-prime cordial labeling is called a k-prime cordial graph. In this paper we investigate 4- prime cordial labeling behavior of complete graph, book, flower, mCn and some more graphs.
R. Ponraj; S. Sathish Narayanan
Abstract
A graph G = (V,E) with p vertices and q edges is said to be a total mean cordial graph if there exists a function f : V (G) → {0, 1, 2} such that f(xy) = [(f(x)+f(y))/2] where x, y ∈ V (G), xy ∈ E(G), and the total number of 0, 1 and 2 are balanced. That is |evf (i) ...
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A graph G = (V,E) with p vertices and q edges is said to be a total mean cordial graph if there exists a function f : V (G) → {0, 1, 2} such that f(xy) = [(f(x)+f(y))/2] where x, y ∈ V (G), xy ∈ E(G), and the total number of 0, 1 and 2 are balanced. That is |evf (i) − evf (j)| ≤ 1, i, j ∈ {0, 1, 2} where evf (x) denotes the total number of vertices and edges labeled with x (x = 0, 1, 2). In this paper, we investigate the total mean cordial labeling of Cn2, ladder Ln, book Bm and some more graphs.
Gholam Hossein Liaghat; Saeed Zargar Azad
Abstract
Die less explosive forming of circular plates is one of the most useful methods in the industries especially chemical applications. Manufacturing of large vessel's head, multilayer rings and some parts of heat exchangers are the example of applying this method. Many theoretical and experimental researches ...
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Die less explosive forming of circular plates is one of the most useful methods in the industries especially chemical applications. Manufacturing of large vessel's head, multilayer rings and some parts of heat exchangers are the example of applying this method. Many theoretical and experimental researches about examining the explosive forming of simple and single layer plate have been done. The purpose of most studies was prediction of transversal displacement of plate and its profile of deformation with respect to the amount of impulsive load due to the explosion. On the other hand, no study has been done for analysis of behavior of bimetallic plate in the explosive forming process. However it can be easily shown that with some small change in plasto-dynamic equations of a simple plate, the behavior of a bimetallic plate in explosive forming process would be analyzed. The used methods in analysis of plasto-dynamic behavior of plates can be divided up to two categories. Some of them have used the equations of motion and wrote these equations for two or three phases of time. This routine is really complex especially in large deformation problems. In other hand, some researchers have applied energy methods for their analytical purposes. The major advantages of this routine is its simplicity. Because there is not necessary to consider the effect of plastic hinge motion for calculating desired parameters. In this paper, die less explosive forming of bimetallic circular plate is analyzed with “energy conservation law” very simply and comprehensively. It will be shown that with calculating full plastic moment and force of a bimetallic plate, the dynamic-plastic’s equations for the simple plates can be used and the displacement of plate's center and its deformed profile can be predicted. Also the presented model has some special capabilities. For example it considers the effects of bending moments and membrane forces simultaneously. Also it is possible to calculate the influence of rotatory inertia and high strain rate effect on the displacement of plate. Further with this analytical model the effect of various supporting condition and the different shape of profile of pressure can be studied. The accuracy and reliability of presented model will be verified with comparison of experimental results and analytical data. Also die less explosive forming process of bimetallic plate have been simulated with Ansys-Lsdyna software. Comparison of different results approves the capabilities of presented model in this article.
P. Jeyanthi; A. Maheswari; P. Pandiaraj
Abstract
A graph $G$ is said to be one modulo three geometric mean graph if there is an injective function $\phi$ from the vertex set of $G$ to the set $\{a \mid 1\leq a \leq 3q-2\} $ and either $a\equiv 0(mod 3) $ or $ a\equiv 1(mod 3)\}$ where $q$ is the number of edges of $G$ and $\phi$ induces a bijection ...
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A graph $G$ is said to be one modulo three geometric mean graph if there is an injective function $\phi$ from the vertex set of $G$ to the set $\{a \mid 1\leq a \leq 3q-2\} $ and either $a\equiv 0(mod 3) $ or $ a\equiv 1(mod 3)\}$ where $q$ is the number of edges of $G$ and $\phi$ induces a bijection $\phi^{*}$ form the edge set of $G$ to $\{a \mid 1\leq a\leq 3q-2 $ and $ a\equiv 1(mod3)\}$ given by $\phi^{*}(uv)=\left\lceil \sqrt{\phi(u)\phi(v)}\right\rceil$ or $\left\lfloor \sqrt{\phi(u)\phi(v)}\right\rfloor$ and the function $\phi$ is called one modulo three geometric mean labeling of $G$. In this paper, we establish that some families of graphs admit one modulo three geometric mean labeling.
Azam Hamami; Amir Ali Youzbashi; Mohammad Ranjbar; Mohammad Pazouki
Abstract
There are no appreciable amounts of nickel resources in Iran; therefore, secondary resources of this element are to be more considered in future. Spent nickel catalysts that are used in various industrial processes are one of them. For example nickel catalyst that is used in hydrogenation of edible oil ...
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There are no appreciable amounts of nickel resources in Iran; therefore, secondary resources of this element are to be more considered in future. Spent nickel catalysts that are used in various industrial processes are one of them. For example nickel catalyst that is used in hydrogenation of edible oil have large amounts of nickel and they are generally supported on porous materials like silica and alumina. Thus, economically extraction of nickel from these materials is an important subject. Hydrometallurgy is the common method for recovery of nickel by suitable leachant. In this work, different acids such as sulfuric, nitric and hydrochloric are used as the solvent for nickel recovery. The effect of some parameters on the recovery of nickel such as acid concentration, reaction time, temperature and oil existence were studied. The results obtained show that, by leaching spent nickel catalyst at high temperature with nitric acid, extraction of nickel is more than 90%. Furthermore, elimination of oil from spent catalyst with organic solvent increases the nickel extraction. The results of the kinetic analysis of the leaching data for various experimental conditions indicated that the reaction is controlled by diffusion through the catalyst network.
Tal'at Ghomashchi; Zahra Akbari
Abstract
Corn steep water as effluent which arrives in environment from starch processing industry has adverse effects on the environment and also large volume of fresh water is wasted. Corn step water is composed of high concentration of proteins, sugar, starch, vitamin and minerals, so it can be used as substrate ...
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Corn steep water as effluent which arrives in environment from starch processing industry has adverse effects on the environment and also large volume of fresh water is wasted. Corn step water is composed of high concentration of proteins, sugar, starch, vitamin and minerals, so it can be used as substrate for production of biological products. Hence, corn steep water concentration is important task both in environmental consideration and reuse of water. In this study, reverse osmosis membrane was used for concentration of steep water. The pilot consisted of two parts: pretreatment and reverse osmosis membrane. Pretreatment section contains ceramic filter with pore size of 50 micron and polypropylene filter which operates at 3-7 bar pressure. Surface area of reverse osmosis membrane was 1.11 m2 and operating pressure is 250 psi. Results showed that permeate flux is reduced exponentially over time and transmission through the polyamide membrane of calcium ions are less than sodium and potassium ions. For membrane cleaning, at first acid solution (pH= 3.5) and then soda solution (pH= 11-11.5) were used. For removal of microorganism like bacteria from polyamide membrane, acetic acid solution (4000 ppm) or hydrogen peroxide (2000 ppm) could be used. In general, reverse osmosis system with polyamide membrane is suitable process for concentration of steep water.
Sohrabali Ghorbanian; Hossein Abolghasemi; Mohammad Ali Mousavian; Sa'eed Reza Radpour
Sa'eed Badagh Abadai; Mehdi Moosavi; Jalal Moosavi
Abstract
Mansuri oil field, which is located at the South-West of Iran, has sand production problem and primary analyses proved the existence of this phenomenon in this field. Generally, there are three methods to evaluate the sand production state which are empirical, numerical, mathematical, and physical. Considering ...
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Mansuri oil field, which is located at the South-West of Iran, has sand production problem and primary analyses proved the existence of this phenomenon in this field. Generally, there are three methods to evaluate the sand production state which are empirical, numerical, mathematical, and physical. Considering the numerical capability to analyze complex geometries under high stresses condition, FLAC3D, which is a three-dimensional explicit finite-difference program for engineering mechanics computation, was employed to analyze sand production in this field. First, the numerical model was calibrated using designed physical model and then, producing intervals and their perforations were modeled by numeric software. Its results showed that not only end-perforation instability is not the sole dominant mechanism in sand production, but also the effect of adjacent perforations on each other is more important. In this respect, there is an optimum pressure that causes perforations failure and catastrophic sand production. Mansuri field analyses demonstrated that the downhole pressure at its wells is near predicted optimum pressure and producing intervals are going to catastrophically produce sand.
Ali Reza Azmoudeh Ardalan; Marzieh Jafari
Abstract
In this paper a practical method for tropospheric effects on GPS derived coordinates in absolute mode is presented. GPS observations at the permanent GPS stations can be used as source of information for the modeling. The developed model is a time-dependent model and as such differs from usual tropospheric ...
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In this paper a practical method for tropospheric effects on GPS derived coordinates in absolute mode is presented. GPS observations at the permanent GPS stations can be used as source of information for the modeling. The developed model is a time-dependent model and as such differs from usual tropospheric models, which are based on atmospheric parameters, i.e. temperature, pressure and humidity. Tropospheric effect on the GPS signals are a source of error, which cannot be eliminated via dual frequency observations. In the other words troposphere is a non-dispersivences environment and therefore, unlike the ionospheric refraction, the effect of tropospheric on the absolute positions cannot be eliminated based on dual frequency observations. What we are presenting in this paper is an operational method for reduction of tropospheric refraction error of the GPS signals, based on continues GPS observations at the permanent GPS stations. The algorithmic procedure of the developed method begins with the processing of the GPS observations at the permanent GPS station according to following procedure: (1) Processing the GPS observations based on dual carrier phase technique (to remove/reduce the effect of ionospheric error and to obtain more precise coordinates based on carrier phase observations with resolived ambiguity). (2) Application of broadcast ephemeris to remove/minimize the satellite position errors. (3) Application of precise satellite clock correction to remove/minimize satellite clock errors. In this way the major sources of GPS errors are removed/minimized and the computed coordinates of the permanent GPS station are mainly affected by the tropospheric refraction. Since, the permanent GPS stations can provide us with long-term continual GPS observation, having available the precise coordinates of the permanent GPS station via precise differential GPS positioning, we are able to develop a time series of the difference between the precise coordinate of the station and the coordinates obtained based on aforementioned procedure. Next, we can subject the resulted time series, which reflects the tropospheric error in combination of random errors, to a FFT process to decompose the time series into a constant and harmonic parts. The constant and the harmonics parts can consequently be fed into a least squares adjustment as the initial value to compute the least square estimates of the constant and time dependent part of the tropospheric corrections in terms of sine and cosine base functions. In this way a tropospheric model can be developed, which is a function of time. Using the whole observations within the year 2000 of the permanent GPS station of National Cartographic Center (NCC) of Iran, located in Tehran/Iran a tropospheric model was developed according to the explained procedure. The computed model was subjected to validity test at the permanent GPS station and also at various locations with different distances to the permanent GPS station. The results can be summarized as follows:
1. Tropospheric error can be detected and modeled according the prescribed procedure due to its time repetition property.
2. The developed model can correct the tropospheric error up to 99% at the time interval used for the modeling (modeling station), and up to 98% for the observations made at the modeling station 2 years after.
3. The developed model is very much local dependent and for that reason for a station located at 1m distance to the modeling station can only remove 52% of the tropospheric error, however it still can remove 52% of the tropospheric error for the locations at 26, 28, 31, and 32 km distance from the modeling station.
Finally, we can conclude that the developed model can be very useful for real-time applications such as navigation and also implementation in the DGPS correction.
