Mohsen Naghibi; Morteza Kolahdouzan
Abstract
A two-dimensional two-phase numerical model is developed to predict transport and fate of oil slicks which resulted the concentration distribution of oil on the water surface. Two dimensional governing equation of fluid flow which consists mass and momentum conservation was solved using the finite difference ...
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A two-dimensional two-phase numerical model is developed to predict transport and fate of oil slicks which resulted the concentration distribution of oil on the water surface. Two dimensional governing equation of fluid flow which consists mass and momentum conservation was solved using the finite difference method on the structured staggered grid system. The resulted algebric equations were solved by use of ADI (Alternating Direction Implicit) technique. In addition the wind speed and coriolis effect can be included in the current hydrodynamic model. Transport of oil slick was pridect by the two dimensinal particle tracking approach consists of Lagrangian method for advection processes, the Random Walk technique for horizontal diffusion process and the empirical equations for the fate processes. Different processes are considered and included in the developed model which are: advection, spreading, turbulent diffusion, evaporation, dissolution, vertical dispersion, emulsification, shoreline deposition and adsorption by bed sediment. Oil is divided into eight hydrocarbon components so this model is capable of considering the oil composition of some fractions with theirs characteristics. Comparison of results with analytical solution for standard problems represent a good degree of similarity. In addition, model is used in a case of oil spill in Persian Gulf to represent the application of model to real case studies.
Hassan Taghizadeh; Mehrdad Tarafdar Hagh
Abstract
This paper presents a new method to find the optimum switching angles in voltage source multilevel converters in order to minimize specific higher order harmonics and decrease the total harmonic distortion (THD) of their output voltage waveform. The output voltage waveform of inverter can either be in ...
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This paper presents a new method to find the optimum switching angles in voltage source multilevel converters in order to minimize specific higher order harmonics and decrease the total harmonic distortion (THD) of their output voltage waveform. The output voltage waveform of inverter can either be in the form of staircase or PWM. In order to increase the degrees of freedom and elimination of more harmonics, one can increase the number of levels or use PWM waveform which has more switching than once at each level. However, both of them result in complexity of nonlinear transcendental equations which solving them by using conventional numerical iterative techniques such as Newton-Raphson method is not feasible. In this paper, particle swarm optimization algorithm is presented to find optimum switching angles of PWM waveform in multilevel converters. These angles must be determined so that the desired fundamental harmonic is maintained and at the same time undesired higher order harmonics are suppressed. Theoretical and simulation results for an eleven-level converter show the efficiency of the proposed algorithm to determine the optimum angles in order to decrease the undesired harmonics and produce very high quality output voltage waveform.
Ardeshir Ahmadi; Azizollah Memariani
Abstract
Bargaining Power is one of the important issues in oil trade negotiations. In this paper two effective factors in bargaining power i.e. patient time to deal and outside options of each player have been considered. The necessary relations for exchange of sources in negotiation have been derived.
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Bargaining Power is one of the important issues in oil trade negotiations. In this paper two effective factors in bargaining power i.e. patient time to deal and outside options of each player have been considered. The necessary relations for exchange of sources in negotiation have been derived.
Sara Farhangi; Mojtaba Shariati Niasar; Mohammad Soltanieh; Mehdi Pourafshari Chenar
Abstract
It is several decades that the application of membrane processes for gas separation has become a great concern within industries. Among them, the polymeric membranes of different structures have played the most important role. Such application has been widely extended to gas separation and due to the ...
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It is several decades that the application of membrane processes for gas separation has become a great concern within industries. Among them, the polymeric membranes of different structures have played the most important role. Such application has been widely extended to gas separation and due to the necessity of both; prediction of the behavior of these processes and recognition of the effective parameters on membrane processes, in this research a mathematical model of mass transfer through polymeric asymmetric membranes is presented. Within the dense section of the membrane, a dual sorption model is applied, while for the porous section, the average effect of the four flow mechanisms; namely Knudsen, viscous, slip as well as surface flow are implemented. Basing on the experimental values of gas permeances through different membranes and by using a proper optimization method, the available membrane transport parameters were determined.
Behrokh Hosseini Hashemi; Rouhollah Ahmadi Jazani
Abstract
Panel zone is one of the most important elements for transferring the lateral load to other elements in Steel Moment Resistant Frames. To some extent, this element through its suitable ductile behavior with beams, that themselves have been known as ductile elements, can increase the overall ductility ...
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Panel zone is one of the most important elements for transferring the lateral load to other elements in Steel Moment Resistant Frames. To some extent, this element through its suitable ductile behavior with beams, that themselves have been known as ductile elements, can increase the overall ductility of SMRF. The suitable design procedure for this element and details, can highly affect the performance of SMRF. Present research, specially on panel zone with unequal beam depth on two sides of panel zone and their effect on panel zone when monotonic load acting on SMRF is limited. Therefore, main aim of this paper is considering ductility of panel zone individually with unequal beams depth on two sides.
The research method is based on verifying the analytical model, built in ANSYS Finite Element Software, with experimental model in laboratory test. This verification permits us to make different models with variety of geometric parameters of Panel Zone (i.e. depth of beams and thickness of column flange).Then the partial ductility ratio that is driven from backbone curve of cyclic behavior of panel zone used for comparing to presence standard rehabilitation code (fema274).
The obtained results from this research in all of geometric cases will not demonstrate constant ductility ratio as stated in standard rehabilitation code (fema274). Current partial ductility ratio in standard rehabilitation code (fema274) will be overestimated. When the depth of one of the two beams is shallower than the other, the partial ductility ratio of panel zone will decrease .In case of exterior columns (which are connected to only one beam) this ratio will be minimum an
Mehdi Ashjaee; Hossein Shokouhmand; Mehdi Amiri; Touraj Yousefi
Abstract
Laminar free convection heat transfer from vertical and inclined arrays of horizontal isothermal cylinders in air was investigated experimentally and numerically. Experiments were carried out using Mach-Zehnder interferometer and the FLUENT code was used for numerical study. Investigation was performed ...
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Laminar free convection heat transfer from vertical and inclined arrays of horizontal isothermal cylinders in air was investigated experimentally and numerically. Experiments were carried out using Mach-Zehnder interferometer and the FLUENT code was used for numerical study. Investigation was performed for vertical and horizontal cylinder spacing from 2 to 5 and 0 to 2 cylinder diameters respectively. The Rayleigh number based on the cylinder diameter varied between 103and 3×103.The effect of vertical and horizontal cylinder spacing and Rayleigh number on the local heat transfer from each individual cylinder was investigated. It was seen that the local heat transfer coefficient of each cylinder strongly depends on its position relative to the others. This variation of the local heat transfer coefficient was explained by the interaction of plume's temperature and velocity profiles.
Kiumars Mazaheri; Ali Tarokh
Abstract
In this work the effect of the accuracy of a FAE detonation modeling on the generated blast wave is investigated. First, a one-dimensional numerical simulation with a reduced chemical kinetics of C2H2-O2-Ar, involving 25 elementary reactions, is used as the base model. The properties of the blast calculated ...
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In this work the effect of the accuracy of a FAE detonation modeling on the generated blast wave is investigated. First, a one-dimensional numerical simulation with a reduced chemical kinetics of C2H2-O2-Ar, involving 25 elementary reactions, is used as the base model. The properties of the blast calculated with this model is compared with those of simpler models, the similarity solution of Taylor, the constant volume (CV) explosion model, and the CJ-burn model. It is found that the result of Taylor's similarity model is in very good agreement with the result of the base model. The blast properties that calculated with the CJ-burn model are also in close agreement with those of the base and Taylor's models. However, the CV model prediction shows considerable difference with the base model. Considering the computational cost and the accuracy, the Taylor's model is recommended as the favorite model for the calculation of the FAE blast properties.
S. Saadatmand; D. Moazzami; A. Moeini
Abstract
In this paper we proposed a Cellular Automaton based local algorithm to solve the autonomously sensor gathering problem in Mobile Wireless Sensor Networks (MWSN). In this problem initially the connected mobile sensors deployed in the network and goal is gather all sensors into one location. The sensors ...
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In this paper we proposed a Cellular Automaton based local algorithm to solve the autonomously sensor gathering problem in Mobile Wireless Sensor Networks (MWSN). In this problem initially the connected mobile sensors deployed in the network and goal is gather all sensors into one location. The sensors decide to move only based on their local information. Cellular Automaton (CA) as dynamical systems in which space and time are discrete and rules are local, is proper candidate to simulate and analyze the problem. Using CA presents a better understanding of the problem.
Niloofar Aghaieabiane; Henk Koppelaar; Peyman Nasehpour
Abstract
It is well-known that, given inorder traversal along with one of the preorder or postorder traversals of a binary tree, the tree can be determined uniquely. Several algorithms have been proposed to reconstruct a binary tree from its inorder and preorder traversals. There is one study to reconstruct a ...
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It is well-known that, given inorder traversal along with one of the preorder or postorder traversals of a binary tree, the tree can be determined uniquely. Several algorithms have been proposed to reconstruct a binary tree from its inorder and preorder traversals. There is one study to reconstruct a binary tree from its inorder and postorder traversals, and this algorithm takes running time of $ \BigO{\emph{n}^2} $. In this paper, we present $ \proc{InPos} $ an improved algorithm to reconstruct a binary tree from its inorder and postorder traversals. The running time and space complexity of the algorithm are an order of $ \BigTheta{\emph{n}} $ and $ \BigTheta{\emph{n}} $ respectively, which we prove to be optimal. The $ \proc{InPos} $ algorithm not only reconstructs the binary tree, but also it determines different types of the nodes in a binary tree; nodes with two children, nodes with one child, and nodes with no child. At the end, the $ \proc{InPos} $ returns a matrix-based structure to represent the binary tree, and enabling access to any structural information of the reconstructed tree in linear time with any given tree traversals.
Amir Mesrikhani; Mohammad Farshi; Behnam Iranfar
Abstract
Let $S$ be a set of imprecise points that is represented by axis-aligned pairwise disjoint squares in the plane. A precise instance of $S$ is a set of points, one from each region of $S$. In this paper, we study the optimal minimum spanning tree (\textit{OptMST}) problem on $S$. The \textit{OptMST} problem ...
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Let $S$ be a set of imprecise points that is represented by axis-aligned pairwise disjoint squares in the plane. A precise instance of $S$ is a set of points, one from each region of $S$. In this paper, we study the optimal minimum spanning tree (\textit{OptMST}) problem on $S$. The \textit{OptMST} problem looks for the precise instance of $S$ such that the weight of the MST in this instance, maximize (Max-MST) or minimize (Min-MST) between all precise instances of~$S$ under $L_1$-metric. We present a $(\frac{3}{7})$-approximation algorithm for Max-MST. This is an improvement on the best-known approximation factor of $1/3$. If $S$ satisfies $k$-separability property (the distance between any pair of squares are at least $k.a_{max}$ where $a_{max}$ is the maximum length of the squares), the factor parameterizes to $\frac{2k+3}{2k+7}$. We propose a new lower bound for Min-MST problem on $S$ under $L_1$-metric where $S$ contains unit squares and provide an approximation algorithm with $(1+2\sqrt{2})$ asymptotic factor.
Azadeh Sharafibadr; Zahra Nilforoushan
Abstract
We consider the problem of finding the localization of radioactive source by using data from a digital camera. In other words, the camera could help us to detect the direction of radioactive rays radiation. Therefore, the outcome could be used to command a robot to move toward the true direction to achieve ...
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We consider the problem of finding the localization of radioactive source by using data from a digital camera. In other words, the camera could help us to detect the direction of radioactive rays radiation. Therefore, the outcome could be used to command a robot to move toward the true direction to achieve the source. The process of camera data is performed by using image processing and computational geometry algorithms. And the robot is looking for the source in a space with geometrical obstacles. Lots of radioactive accidents daily occur all over the world. During the radiography, the radioactive source is sometimes thrown out from its protection layer and the radiographer has to look for it in the space around. This would have lots of irreparable costs. Thus, it seems necessary to make a robot which could search the radioactive source intelligently.
Iman Shojaei; Hossein Rahami
Abstract
Some near-regular mechanical systems involve global deviations from their corresponding regular system. Despite extensive research on vibration analysis (eigensolution) of regular and local near-regular mechanical systems, the literature on vibration analysis of global near-regular mechanical systems ...
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Some near-regular mechanical systems involve global deviations from their corresponding regular system. Despite extensive research on vibration analysis (eigensolution) of regular and local near-regular mechanical systems, the literature on vibration analysis of global near-regular mechanical systems is scant. In this paper, a method for vibration analysis of such systems was developed using Kronecker products and matrix manipulations. Specifically, the eigensolution of the corresponding regular mechanical system was inserted in the algorithm to further accelerate the solution. The developed method allowed reduction in computational complexity (i.e., $\mathrm{O}(n^2)$) when compared to earlier methods. The application of the method was indicated using a simple example.
Mehdi Shams; Gholamreza Hesamian
Abstract
This paper extends the sign test to the case where data are observations of fuzzy random variables, and the hypotheses are imprecise rather than crisp. In this approach, first a new notion of fuzzy random variables is introduced. Then, the $\alpha$-level sets of the imprecise observations are transacted ...
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This paper extends the sign test to the case where data are observations of fuzzy random variables, and the hypotheses are imprecise rather than crisp. In this approach, first a new notion of fuzzy random variables is introduced. Then, the $\alpha$-level sets of the imprecise observations are transacted to extend the usual method of sign test. To do this, the concepts of fuzzy median and fuzzy sample median are defined.We also develop a well-known large sample property of the classical sample median. In addition, the test statistic is extended for investigating fuzzy hypothesis. After that, applying an index called credibility degree, the degree that the observed fuzzy test statistics belongs to the critical region is evaluated. The result provides a fuzzy test function which leads to some degrees to accept or to reject the fuzzy null hypothesis.A numerical example is provided to clarify the discussions made in this paper.
Toktam Khatibi; Javad Zarean
Abstract
The paper introduces a new method called ABCL-EHI for human identification using electroencephalographic (EEG) signals. EEG signals have unique information among individuals, but current systems lack accuracy and usability. ABCL-EHI addresses this by combining a convolutional neural network (CNN) and ...
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The paper introduces a new method called ABCL-EHI for human identification using electroencephalographic (EEG) signals. EEG signals have unique information among individuals, but current systems lack accuracy and usability. ABCL-EHI addresses this by combining a convolutional neural network (CNN) and a long short-term memory (LSTM) network with an attention mechanism. This attention mechanism enhances the utilization of spatial and temporal characteristics of EEG signals. The proposed system is evaluated using a public dataset of EEG signals from 109 subjects performing motor/imagery tasks. The results demonstrate that ABCL-EHI achieves high accuracy, with F1-Score scores of 99.65, 99.65, and 99.52 when using 64, 14, and 9 EEG channels, respectively. This outperforms previous studies and highlights the system's reliability and ease of deployment in real-life applications, as it maintains high accuracy even with a small number of EEG channels and allows users to perform various tasks while recording signals.
P. Jeyanthi; A. Sudha
Abstract
A vertex irregular total k-labeling of a graph G with vertex set V and edge set E is an assignment of positive integer labels {1, 2, ..., k} to both vertices and edges so that the weights calculated at vertices are distinct. The total vertex irregularity strength of G, denoted by tvs(G)is the minimum ...
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A vertex irregular total k-labeling of a graph G with vertex set V and edge set E is an assignment of positive integer labels {1, 2, ..., k} to both vertices and edges so that the weights calculated at vertices are distinct. The total vertex irregularity strength of G, denoted by tvs(G)is the minimum value of the largest label k over all such irregular assignment. In this paper, we study the total vertex irregularity strength for n ≥ 3, m ≥ 2, Pn ⊙ K1, Pn ⊙ K2, Cn ⊙ K2, Ln ⊙ K1, CLn ⊙ K1, P2 ⊙ Cn, Pn ⊙ Km, Cn ⊙ Km
Akbar Eshaghi; Jafar Raiszadeh; Hamid Reza Ghasemi; Reza Taghiabadi
Abstract
The effect of T6 heat treatment on the microstructure and wear behavior of Al-332 piston alloy containing 1.2wt% iron was investigated. The results showed that the T6 heat treatment changed the morphology of acicular eutectic Si particles to a more spherical form. The heat treatment also reduced the ...
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The effect of T6 heat treatment on the microstructure and wear behavior of Al-332 piston alloy containing 1.2wt% iron was investigated. The results showed that the T6 heat treatment changed the morphology of acicular eutectic Si particles to a more spherical form. The heat treatment also reduced the average length and blunted the needle-like ?- phase intermetallics through dissolution and fragmentation. The results also showed that an increase in the time and temperature of the heat treatment decreased the length of the ?-phase by about 70 percent and further blunted it at solutionizing temperature of 520?C for 14h. The results also showed that heat treatment increased the wear resistance of the alloy by about 40 percent.
R Ponraj; J Maruthamani; R Kala
Abstract
In this paper we introduce a new graph labeling method called $k$-Total prime cordial. Let $G$ be a $(p,q)$ graph. Let $f:V(G)\to\{1,2, \ldots, k\}$ be a map where $k \in \mathbb{N}$ and $k>1$. For each edge $uv$, assign the label $gcd(f(u),f(v))$. $f$ is called $k$-Total prime cordial labeling of ...
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In this paper we introduce a new graph labeling method called $k$-Total prime cordial. Let $G$ be a $(p,q)$ graph. Let $f:V(G)\to\{1,2, \ldots, k\}$ be a map where $k \in \mathbb{N}$ and $k>1$. For each edge $uv$, assign the label $gcd(f(u),f(v))$. $f$ is called $k$-Total prime cordial labeling of $G$ if $\left|t_{f}(i)-t_{f}(j)\right|\leq 1$, $i,j \in \{1,2, \ldots, k\}$ where $t_{f}(x)$ denotes the total number of vertices and the edges labeled with $x$. We investigate k-total prime cordial labeling of some graphs and study the 4-total prime cordial labeling of path, cycle, complete graph etc.
Hamid Reza Shahverdi; Manouchehr Haghighi; Kazem Fouladi
Siamak Motahhari
Abstract
In the present research work, the flexural modulus and strength of glass fiber-epoxy resin and carbon fiber-epoxy resin composites have been enhanced through fiber tension during curing of the polymeric resin. This study showed that the tension applied on the fibers increased the flexural modulus of ...
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In the present research work, the flexural modulus and strength of glass fiber-epoxy resin and carbon fiber-epoxy resin composites have been enhanced through fiber tension during curing of the polymeric resin. This study showed that the tension applied on the fibers increased the flexural modulus of the glass-epoxy composites up to 12% and the flexural strength up to 19%. The flexural modulus and strength of carbon-epoxy were also increased up to 25% and 13%, respectively. It was shown that the optimum fiber tension to obtain the maximum flexural properties depends on the fiber the composite is made of. The mechanism through which the improvement has been achieved was also presented.
Majid Meybodian; Hossein Memarian; Mehdi Zare
Abstract
Sarcheshmeh copper mine, with the final reserves of 828 million tons of sulfur ore and average grade of 0.74%, is known to be the largest open pit of Iran and most probably the second largest copper mine in the world. This mine is located in the seismotectonic zone of Central-Iran, and 23 Km away from ...
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Sarcheshmeh copper mine, with the final reserves of 828 million tons of sulfur ore and average grade of 0.74%, is known to be the largest open pit of Iran and most probably the second largest copper mine in the world. This mine is located in the seismotectonic zone of Central-Iran, and 23 Km away from the 150 Km long Rafsanjan active fault.In this study the vulnerability of the west wall of the mine, which is more susceptible to sliding, is determined. First, the seismic hazard probability was calculated by defining seismic sources and determination of seismicity parameters. Then the most effective source in seismic hazard is determined by seismic hazard deaggregation. The Newmark displacement of the west wall is calculated by the critical acceleration and Arias intensity. Finally, the mine vulnerability and seismic risk for this site, along with the probable earthquakes, is calculated. The seismic risk of this site is estimated to be 0.07 of the overall value of the mine.
Mohammad Farough Hosseini; Soroush Fouladchi; Mojtaba Ganji
Abstract
Wave propagation is used as an advanced tool of determining elastic properties of rocks. In spite of being cheap and non destructive tests of rock mechanics, due to its modernity method is not yet replacing the traditional dear and destructive tests. In order to pave ways of replacing this test and making ...
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Wave propagation is used as an advanced tool of determining elastic properties of rocks. In spite of being cheap and non destructive tests of rock mechanics, due to its modernity method is not yet replacing the traditional dear and destructive tests. In order to pave ways of replacing this test and making best use of it all effective factors of such method are to be assessed. One fundamental factor affecting the test result is the shape of the specimen tested. The existing standards do not seriously take the sample shape into consideration. It was pointed out elsewhere that in spite of popular taught elastic dynamic properties do vary seriously due to variation of sample shape (height to diameter ratio). As this fact was revealed for limestone in our previous investigation this assessment was extended to other types of rocks for the possibility of true judgment. Therefore, ultrasonic wave propagation tests were conducted on four various rock types with height to diameter ratio of 0.5 to 3. Analyzing of the test results showed that shear wave velocity and elastic dynamic constants are noticeably dependent on sample height/diameter ratio. The variation of height/diameter ratio from 0.5 to 3 caused the variation of shear wave velocity and Poisson’s ratio up to 70%, Elasticity modulus up to 160% and shear modulus up to 200% as follows in details:
Variation in shear wave velocity: Limestone, 24%; Siltstone, 70%; Green Tuff, 17% and Granodiorite, 20%.
Variation in dynamic elastic modulus: Limestone, 26%; Siltstone, 65%; Green Tuff, 73% and Granodiorite, 33%.
Variation in Poisson’s ratio: Limestone, 45%; Siltstone, 160%; Green Tuff, 20% and Granodiorite, 35%.
Variation in shear modulus: Limestone, 53%; Siltstone, 200; Green Tuff, 38% and Granodiorite, 45%.
It was also observed that the longitudinal wave velocity was not following the height/diameter ratio and showed no specific trend of variation.
As seen from the above details, the variation of modulai is much grater for siltstone in compares to the 3 other rocks. It is most likely that this obvious difference is due to inhomogenity of the siltstone texture which causes different behavior in this particular rock.
Hamideh Cheraghi; Behzad Vosoghi
Ali Reza Azmoude Ardalan; Abdorreza Safari; Yahya Tavakkoli
Abstract
The methods applied to regularization of the ill-posed problems can be classified under “direct” and “indirect” methods. Practice has shown that the effects of different regularization techniques on an ill-posed problem are not the same, and as such each ill-posed problem requires its own investigation ...
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The methods applied to regularization of the ill-posed problems can be classified under “direct” and “indirect” methods. Practice has shown that the effects of different regularization techniques on an ill-posed problem are not the same, and as such each ill-posed problem requires its own investigation in order to identify its most suitable regularization method. In the geoid computations without applying Stokes formula, the downward continuation based on Abel-Poisson integral is an inverse problem, which requires regularization. Since so far the regularization of this ill-posed problem has been thoroughly studied, in this paper the regularization of the downward continuation problem based on Abel-Poisson integral, is investigated and various techniques falling into the aforementioned classes of regularizations are applied and their efficiency is compared. From the first class Truncated Singular Value Decomposition (TSVD) and Truncated Generalized Singular Value Decomposition (TGSVD) methods and from the second class Generalized Tikhonov (GT) with the norms and semi-norms in Sobolev subspaces , are applied and their capabilities for the regularization of the problem is compared. Our numerical results derived from simulated studies reveal that the GT method with discretized norm of Sobolev subspace gives the best results among the studied methods for the regularization of the downward continuation problem based on the Abel-Poisson integral. On the contrary, the TGSVD method with the discretized second order derivatives has less consistency with the ill-posed problem and yields less accuracy. Finally, the GT method with discretized norm of Sobolev subspace is applied to the downward continuation of real gravity data of the type modulus of gravity acceleration within the geographical region of Iran to derive a geoid model for this region.
Ahmad Aftabi Sani; Vahid Lotfi
Fereydoun Sabet Ghadam; Vahid Esfahanian; Mohammad Eftekhari Yazdi
Abstract
Capability of the Proper Orthogonal Decomposition (POD) method in extraction of the coherent structures from a spatio-temporal chaotic field is assessed in this paper. As the chaotic field, an ensemble of 40 snapshots, obtained from Direct Numerical Simulation (DNS) of the Kuramoto-Sivashinsky (KS) equation, ...
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Capability of the Proper Orthogonal Decomposition (POD) method in extraction of the coherent structures from a spatio-temporal chaotic field is assessed in this paper. As the chaotic field, an ensemble of 40 snapshots, obtained from Direct Numerical Simulation (DNS) of the Kuramoto-Sivashinsky (KS) equation, has been used. Contrary to the usual methods, where the ergodicity of the field is needed, the ensemble members are generated directly by disturbing the initial conditions in a random fashion. The POD eigenvalues and eigenmodes are extracted, using the POD/SVD technique and an ensemble averaging process is performed on the resulting modes, which are used in reconstruction of the field. The resulted mean field is compared with the Fourier mean field as well as the original (instantaneous) field. The results strictly have shown presence of non-coherent parts in the POD reconstructed field, which can be interpreted as the POD weakness in the filtering of the random part of the field. On the other hand, the ensemble averaged POD modes had obvious superiority, in comparison with the mean Fourier modes, in tracing of the mean behavior of the field and the mean temporal gradients. As a consequence, use of the ensemble averaging in the POD modes can be suggested, at least in some spatio-temporal the fields with dominant coherent structures.
