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The estimation of velocity distribution plays a major role in the hydrodynamics of vegetated streams or rivers of extensive natural floodplains. The velocity profile in vegetated channels can be divided into three zones: uniform zone which is close to bed with uniform velocity distribution, logarithmic zone which involves the main channel with no vegetive cover and the transition zone that is affected by the upper zone flow. In order to arrive at an analytical solution to the force balance that governs the flow specific turbulence, characteristics of the flow through the vegetation are required. A new analytical model for the velocity distribution in the transition zone of vegetated (inflexible submerged vegetation) channels is hereby developed. The model is based on a force equilibrium equation and on Prandtl Mixing Length concept. Vegetation is treated as a homogeneous field of identical cylindrical stems and the flow field considered as uniform and steady. The proposed procedure is straightforward; it follows principles of fluid mechanics and shows good agreement with laboratory flume experiments. The new model can be employed for an exact estimation of discharge through naturally vegetated rivers. The model has been calibrated and verified. The results imply a desirable correlation between calculated and observed data.

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The high frequency of the linguistic tools of the anthropomorphic metaphor in the Qur'an not only provides the ground for the deviation of monotheism and monotheistic truths, but also it can pave the way to the facts of the spiritual world, the mysteries of the unseen world, and the intellectual and spiritual truths clarify in the light of conceptual theory. The most important goals of this study are to elucidate the types of Qur'anic anthropomorphism, to explain their mechanism of formation, to analyze the specific conceptualizations behind each of these metaphors and their semantic motivations for their application. The result showed that the application of anthropomorphic metaphors, in addition to reducing complex intellectual and abstract / immanent affairs to the human scale, they reinforce the vital and abstracted relations of deconstruction, more than any other text that expresses the movement from plurality to the spiritual unity beyond nature and devoid of exaggeration, degradation or exaggeration in praising or blaming. The discovery of attention in these metaphors, which are often one of the most prominent human traits, confirms the necessity of applying the mixed model.
 
1. Introduction
The language of the Qur'an, like the language of other religious and literary texts, contains natural phenomena and high-frequency and abstract concepts, the various tools have been used, such as metaphor to facilitate the transmission of these phenomena and concepts to the audience and the perception of these phenomena and concepts. In the Romantic view, metaphor is a testament to the role of imagination in conceptualization and reasoning, and it is not limited to the language of literature. This view has found a special place in the research of cognitive linguists such as Gilles Fauconnier and Mark Turner, the perception of imagination role in language and the process of meaning-making especially the "creative" aspects of meaning construction, such as an innovative metaphor, meta-normality (deviated from the principle), eventually led to the emergence of conceptual blending theory.
In this regard, anthropomorphism or anthropomorphic metaphor can be considered as a cognitive practice, more than any kind of metaphor that is actually the result of human mental imagination and the induction into anything; because in the light of the theory of integration, on the one hand, two seemingly alien elements are intertwined and create ambiguity, and on the other hand, the unfamiliar element is represented in the new perspective with the help of the familiar element. In other words, this theory shows the mechanism of the formation meaning in the mind.
 
2. The Statement of Problem
Anthropology is derived from the Greek root anthropus "human" and the logos link "speech, cognition" (Panoff and Pern, 1973, translated by Askari Khaneghah, 1369: 22) According to this definition in the field of art and literature, to anything other than existence and human nature (living and inanimate), such as animals, plants, inanimate objects and even natural phenomena and changes (day, night, wind, rain and storm, etc.), human characteristics such as body shape, appearance, feelings, sounds, accents, etc. are induced (Asnaashari and Sadeghian, Hakak, 1398: 258-287).
This type of metaphor can be studied and analyzed with the help of the conceptual theory of " Conceptual Blending Theory ". According to the conceptual cognitive process, human beings can subconsciously take the structures from one domain or input, integrating it into a kind of coherent information construction with the elements of another domain / input in "generic space". In such an approach, a new mental space is created in which one domain is merged with another domain based on imagination or in other words, through "conceptual projection" (Moazani and Khanjari, 2014: 4-5; Ardabili et al., 2015: 36; Geertz, 2009, Safavid translation, 1393: 432). Thus, the unusual concepts that violate the general and real logic of human beings they use a mixed process to give birth to new meanings (Moazani and Khanjari, 2014: 4-5).
Anger is a natural reaction of an organism to a situation in which a person fails, which in verse 154 of Surah A'raf, "But you are silent about Moses of anger," is interpreted in a human way.
In this verse, the verb "silent", which is a human act, is attributed to one of the inner states of man, namely "anger". According to Ghaeminia (1396: 319), anger seems to be assumed as a minor human being within the Prophet Moses (pbuh). When a person becomes angry, it is as if someone appears inside him who commands him to do things.
According to the mixed theory, the above documents show two domains of origin; The first realm is human and the second realm is the inner state of internal anger. As a result of the fusion of two realms, a mixed realm is obtained in which anger is portrayed as a human being who can speak and remain silent. Undoubtedly, the use of anthropomorphism in this verse and the personification of anger have beautifully illustrated human’s control when he is angry. When a person becomes upset, he loses control, so it is his anger that manages his behavior and forces him to engage in an inappropriate, emotional, and unconventional behaviors. This is an important psychological principle that the glorious Word refers to by applying the concept of personification.
 
3. Purpose, Questions and Hypotheses
The language of the Qur'an is full of unique and abstract concepts that have been presented to the audience using the anthropomorphic metaphors comparing to the human language. The nature, abstractions, and natural reactions of the organism are some of these concepts. It seems necessary to study these concepts in order to explain the mechanism of their metaphors and to discover the specific conceptualization behind each of these concepts in order to reveal another part of the expressive miracle of the Qur'an. Accordingly, the present study tries to examine those Qur'anic evidences in which inhuman concepts have been conceptualized with the help of human semantic components to answer the following questions:
1. What is the purpose of applying the mixed theory to the meaning of anthropomorphic metaphors in Qur'an?
2. What are the semantic motives for using anthropomorphism in Qur'an?
The hypotheses considered are as follows:
-The application of this theory in Qur'an, like other texts, clarifies the existence of the human features in metaphors. It also shows the importance of compounds in the discovery of focus.
-Anthropomorphism in Qur'an is often done to show the spiritual dimension of nature and transcendental phenomena, as well as the movement from plurality to unity.
 
4. Methodology
The present study seeks to determine the mechanism of formation of Qur'anic anthropomorphic metaphors in expressing abstract concepts in a scientific and methodical manners by using the interdisciplinary method of "conceptual compounds" in Qur'anic studies. Regarding the fact that one of the important tools of researchers in the field of humanities is books, the tools of this article are shaped by the glorious words and Quranic data and dictionaries and commentary books.
 
5- Results
In this study, the concept of anthropomorphism as one of the linguistic domains of the discourse of the Holy Quran was studied and analyzed according to the theory of " Conceptual Blending Theory " and while showing some verses that:
The theory of "blending" is a new and wonderful tool for analyzing the linguistic interpretations of Qur'an, including similes, allegories, metaphors, anthropomorphisms, allusions, and so on. This theory, in addition to explaining the mechanism of origin of these meanings, enhances the power of cognitive analysis, and opens the new perspectives in the mind of the interpreter and reveals the hidden dimensions of the linguistic interpretations of the Qur'an in the better way.
-The theory of "blending" pursues several goals, but the common goal of all blends and compounds are to achieve a human features. This goal is very important in the analysis of Qur'anic integrations, because the Holy Qur'an has explained many intellectual truths, divinity, occult unknowns and abstract concepts using the tangible human experiences appropriate to the audience. Another purpose of applying the conceptual blending theory is that it is importance in discovering the center of metaphorical meanings and strengthening the vital and abstract relations.
-Anthropomorphism in the Qur'an is often done to show the spiritual dimension of nature and transcendental phenomena, as well as to move from plurality to unity away from excesses in magnification, degradation or exaggeration in praise or condemnation, and so on

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Because of the low Reynolds numbers in microchannels, using of micromixers to improve the flow mixing is essential. Therefore, in this study mixing in nine different micromixer geometries, such as: simple T-shaped micromixer, micromixer with rectangular or parallelogram ribs on the walls of the mixing channel, T-shaped micromixer with two additional parallel or perpendicular inlet channels, micromixer with circular or triangular barriers in the middle of the mixing channel, rhombus micromixer with thick or thin edges, has been investigated. Sinusoidal oscillatory velocity with a phase difference of 180 degrees relative to each other has been applied to channels inlet. The governing equations have been solved numerically using the finite volume method. For all geometries time variation of mixing degree at microchannel outlet and the variation of mixing degree along the channel length have been computed. Results show that for micromixers, which divide the flow to several layers such as rhombus micromixers, mixing degree is high and the micromixers with ribs on the walls have lower mixing degrees. Also, there is an optimum frequency at constant average velocity in which the mixing degree has its highest value.

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In the present study, the mixing fluids flow in the twin and circular mixers is investigated by using an improved robust weakly compressible Smoothed Particle Hydrodynamics method. In order to remove the Smoothed Particle Hydrodynamics complications and according to a predictive corrective scheme, a robust modified algorithm which uses the advanced second order discretization, pressure velocity decoupling, kernel gradient corrections and shifting algorithm is offered. After the verification and validation of the present algorithm for the moving boundary problems, the present algorithm is applied for investigation of the mixing behaviors of the two-blade circular and twin chamber mixers. By investigation of the mixing paths, the proper geometry for the two-blade mixers is proposed and examined. The effects of the rotation direction of the blades, geometry and Reynolds number on the mixing rate are investigated. The results show that the twin chamber mixer can improve the mixing performance over 60% in comparison with the circular chamber mixer while the case with circular chamber and same direction rotation of the blades has the weakest performance among the cases which have been examined.

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Using CFD, the effect of burner angle on an aluminum rotary furnace performance is studied in the present study. Turbulent non-premixed combustion of natural gas and oxygen, radiation, furnace rotation, aluminum smelting and aluminum burn-off are considered in the proposed numerical model. According to the distinct phenomena occurring in an aluminum rotary furnace, the model divides the furnace into three zones: refractory lining, combustion zone and melt zone. Only heat can be transferred through interfaces of zones and mass transfer through them is not considered in such furnace modeling. Numerical simulations regarding burner angles form 0ᵒ to 15ᵒ revealed that the higher burner angles enhance the fuel and oxygen mixing and increases the resident time of combustion gases in the furnace atmosphere, which consequently improve the furnace performance and lower the aluminum melting rate. However, the simulation results also showed that burner angles more than 10ᵒ are not applicable due to refractory lining overheat. It was showed eventually that changing burner angle from 0ᵒ to 10ᵒ decreases furnace operation time by 35 minutes and increases furnace thermal efficiency from 65% to 74.7%.

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Dissemination of an analyte under the laminar flows plays a major role in measuring and assessment of biological fluids such as sample preparation in the context of microfluidic systems. Due to the development of manufacturing technology in the Lab-on-a-chip devices, the production of rectangular microchannels with finite aspect ratios and micron and submicron sizes has been provided by which the effect of electrokinetic phenomena on concentration distribution will be magnified in these systems. Since the recent researches in this field have overlooked such effects, the present work will be conducted analytically to study the effect of electric double layer on cross stream diffusion of the analyte in the combined electroosmotic and pressure driven flows. Three flow scenarios, the favorable, adverse and zero pressure gradients are analyzed. The results demonstrate that the width of the diffusion region near the top and bottom walls of the microchannel becomes broader with the increase in the Debye length. Also, the results of the scaling analysis reveal the decrease in mixing intensity with increasing the Péclet number based on Helmholtz-Smoluchowski velocity and dimensionless Debye–Hückel parameter. As well, the average scaling exponent of this criterion is a descending function with respect to the thickness of the electric double layer.

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Mixing within electrokinetic micromixers is studied numerically in this article. Micromixer studied here is simply a heterogeneous parallel plate microchannel which is imposed to the electroosmotic flow field. For the through modeling of such flows, the coupled equations of Navier-Stokes, Nernst-Planck, Poisson-Boltzmann and concentration equations are solved for the flow motion, electric charges transport, electric field and species concentrations, respectively. Numerical solution of these set of equations for the heterogeneous microchannels is complicated and difficult. Therefore, simple and approximate model such as Helmholtz-Smoluchowski has been proposed which is basically appropriate for the case of microchannels with the homogenous properties on the walls. Validation of Helmholtz-Smoluchowski model is well-examined for the prediction of two dimensional flow fields, yet its applications is rarely validated for the prediction of concentration field and mixing performance. In this article mixing due to electroosmotic flow field is investigated using Nernst-Planck equations as well as Helmholtz-Smoluchowski models and the accuracy of the Helmholtz-Smoluchowski model is evaluated. Comparison of the results indicates that for the proper conditions, approximate model can predict the mixing performance accurately along the micromixer length.

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In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. In this paper, the flow field between two straight groynes in shallow wide open channel has been measured using Particle Image Velocimetry method. Groynes with 25cm length, 5cm width and 7cm height with two aspect ratios of 1 and 2 have been located in the fully developed zone of a 18m length flume and velocity measurements carried out in order to study the circulating flow, structure of the mixing layer and downstream separation zone. Image processing is conducted using GPIV software and Westerweel and Brevis methods are used for filtering of the measured velocity fields. Results are presented in form of time averaged values, turbulence intensities and Reynolds stresses at various zones of the groyne field. Results showed that due to the flow shallowness, most of the turbulent structures are two dimensional. Development of a back flow from downstream zone to the groyne field enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration. enhances the complexity of the mixing layer and mas exchange phenomenon compared to the groyne series configuration.

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Since the majority of fluids in engineering and biologic applications are non-Newtonian, the study on mixing of non-Newtonian fluids is very important. Secondary flows are used in curved micromixers to improve the mixing of fluids. In this study, a numerical study was performed on the mixing of non-Newtonian fluids in curved micromixers using Open source CFD code of OpenFOAM. The flow was assumed three-dimensional, steady and incompressible and Reynolds numbers were between 0.1-300. Also, water and CMC solution were used for simulation of Newtonian and non-Newtonian fluid flows, respectively. The effect of Reynolds number, power-law viscosity parameters and micromixer geometry on mixing index and non-dimensional pressure drop was studied and results were compared with those of the straight channel micromixer. The results showed that the mixing index decreased by decreasing the power law index. The mixing index was high for shear thinning flows in micromixers with sharp turns. Also, by increasing the Reynolds number, and therefore velocity, centrifugal force effects increased and mixing improved. Simultaneous investigation of mixing index and pressure drop showed that for low Reynolds numbers and small power law indexes micromixer-b had better performance.

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In this present study, the mixing of two incompressible miscible fluids with different density and viscosity has been investigated in a two-dimensional microchannel equipped with an oscillating stirrer in different excitation frequency. Although most studies in the field of fluid mixing, have been studied the mixer performance when the two fluids were absolutely identical, but the mixing make sense when two fluids has been non-uniformity such as different temperature, concentration or properties. The aim of this study is to evaluating the effect of various properties of the fluids in mixer performance and mixing value. Simulation has been performed in Re=100 and Sc=10, between 0.1 to 1 strouhal number by using element based finite volume method by means of commercial code CFX. Mixer performance has been evaluated in three different modes: mixing of two identical fluids, mixing of two fluids with different density and mixing of two fluids with different viscosity. The results show that, mixing of the fluids with different properties leads to change in mixer performance, and has unique performance in each case. In comparison with similar properties fluids, mixing of fluids with different viscosity and density show lesser inclined in mixing. It has been shown that variation of strouhal number has lesser effect on mixing index changes. The ratio of maximum mixing index changes to base mixing index in the case of different density and viscosity is 54.01 and 51.15 percent, respectively, while the value is 577.94 percent for the mixing of similar fluids.

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The aim of this study is to compare the performance of floor displacement and overhead mixing ventilation systems in providing the thermal comfort conditions for bus passengers. For this reason, the flow and energy have been numerically simulated inside a Scania 4212 bus with its 45 passengers. In the case of displacement ventilation, the inlet diffusers have been located under the seats at the floor and for mixing ventilation mode, the inlet diffusers have been established overhead of passengers. In both cases, as mentioned in ASHRAE standard for public transportation, the inlet air rate of 5 lit/s has been provided for each passenger and the inlet air temperature has been controlled until the predicted mean vote index is within the allowable range of thermal comfort standards. In displacement ventilation because of locating the inlet diffusers on the floor and the buoyancy effects, the air temperature in foot region is about 18C, which is lower than other parts of body and vertical temperature difference in overhead mixing ventilation occurred less than floor displacement ventilation and the temperature difference between foot and head region is only 2C. In overhead mixing ventilation, air temperature near the head is about 24C while in floor displacement ventilation the temperature is about 26C that is not in neutral zone. The results of 65-nodes thermal comfort model indicate that the temperature difference between skin neutral temperatures of each segment in floor displacement mode is higher than overhead mixing ventilation

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Due to easy manufacturing technology and implementation of passive micromixers in a complex microfluidic system, in this study, a type of passive micromixer has been investigated. Passive micromixers increase the mixing rate by increasing the contact surface of two fluids and reducing the distance of molecular diffusion. In the present study, numerical analysis of an L-micromixer has been performed to investigate the mixing behavior and characteristics of fluid flow with changes in key geometrical parameters at four Reynolds numbers. Three non-dimensional geometrical parameters, i.e., normalized length (ZR), length ratio (LR), and aspect ratio (AR) have been defined. Simulations have been performed at the Schmidt number of 900.18. The Reynolds number has been also selected in the range of 50 to 200. A mixing index has been used to quantify mixing behavior in the microchannel. The accuracy of simulation done has been proved by comparing current results with the results of other valid studies. The results reveal that mixing index and pressure drop in a serpentine channel are sensitive to the changes of geometric parameters of the microchannel, and showing different behavior at various Reynolds numbers. Furthermore, due to the sharp 90° turns in the microchannel, the inertial force is large enough to cause vortices, which leads to chaotic advection.

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Slug flow is one the most complicated flow regime in industrial process that is seen for wide range of fluid flow. However, there are always some differences between experimental and numerical results obtained for slug flow. Proceeding the perivious attempt on the selection of the best turbulent model for numerical simulation, the slug flow is simulated numerically in two dimension by applying implicit VOF method and k-ε RNG turbulent model. To extract the slug flow parameters accurately FLUENT solver is used. The differences of the obtained results with and without turbulent model during slugging is also presented. To overcome this complicated flow behavior, a new user defined function code is developed. This UDF computes and predict slug parameters from FLUENT solver result without increasing the computational cost. The important slug parametrs are presented which are: liquid slug body velocity, liquid film velocity, slug front and tail velocity, slug center position and length, slug front and tail positions, pressure difference across slug, wall shear stress, slug mixture velocity, slug initiation time and position from the duct inlet. These parameters are analyzed and discused in details after that they had been validated

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In this article, mixing in the combined electroosmotic/pressure driven flows of non-Newtonian fluid in a microchannel with rectangular obstacles and non-homogeneous ζ-potential has been studied numerically. The non-Newtonian behavior of the fluid is considered for the flow field using power law rule. Also, the nonlinear Poisson-Boltzmann equation is used to model the distribution of ions across the channel and the electric potential. Numerical solutions of coupled equations of momentum, electric field and concentration field are performed by means of finite element method. In this study, the effects of various parameters such as pressure gradient, rheological behavior of the fluid and the geometrical and physical parameters of obstacles on the mixing quality are investigated. The results indicate that applying adverse pressure gradient to the flow, the dilatant behavior of the fluid, as well as the height of barriers, are highly effective in the enhancement of the mixing quality within the microchannel. It is found that for microchannels with heterogeneous ζ-potential, increasing the length of obstacles significantly increases the mixing efficiency while for the microchannels with homogeneous ζ-potential, barrier length has a slight effect on mixing efficiency.

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In this study, effects of zeta potential distribution and geometrical specifications are numerically investigated on mixing efficiency in electroosmotic flows. Considered geometries include straight, converging, diverging, and converging-diverging microchannels. Electroosmotic flow simulations are conducted based on the N-S and Nernst-Planck equations for momentum and ionic charges distributions, respectively, by lattice Boltzmann method. Numerical simulations are validated against available analytic electroosmotic flow solutions in homogeneous straight channels, and then flow patterns and mixing performances in the presence of non-uniform zeta potential distributions are investigated in search for enhanced mixing performances. Numerical results indicate that converging channel leads to a sizable increase in mixing efficiencies, while the flow rate decreases at the same time. In contrast, diverging channels increase the flow rate, while decrease the mixing efficiency. Therefore, it is expected to achieve a balance between the mixing efficiency and mass flow rate using converging-diverging geometries. Numerical results indicate that mixing efficiency of about 90% can be reached with a converging-diverging microchannel with a reasonable decrease in mass flow rate as compared to its geometrical diverging-converging counterpart channel.

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Due to the increasing use of concrete and the use of additives in it , research in this direction is very important . Resistance is one of the effective values in the design and control of concrete quality that numerous factors and parameters affect it . Perhaps increasing in concrete mixing time is one of the parameters that are considered less attention and in this research ; the effect of mixing time on compressive strength of Nano - silica concrete with pozzolan rice husk was studied and were compared with concrete without Nano - silica and pozzolan rice husk .Therefore the effect of sulfate to reduce the resistance of this type of concrete was studied and compared . So , a number of pieces of concrete cube with sides of 15 cm contains %1 Nano - silica and 20% pozzolan husk Rice with a time of mixing varies between 10 to 40 minutes , that every 5 minutes , 3 samples of concrete were taken and made in the days 3 , 7 and 28 under the stress test and ultimately the results of mixing different compressive strength by the time was drawn and reported . Rice husk also tested and its components determined and compared with the standard . Nano - silica concrete and concrete pozzolan rice husk and without Nano – silica and pozzolan was also photographed to compare the density of particles , and at the end testing plan was written by Taguchi testing of concrete . The results show that for the most compressive strength of concrete pozzolan Nano comes with rice husk , the right time (optimal) 25 minutes with a Taguchi test results differ by about 9 percent lower than the margin of error is permitted , that at this time the concrete maximum compressive strength shows the maximum compressive strength at 28 days after the concrete 415 kg/cm2 and then does not show significant strength concrete . Pozzolan concrete without silica and rice husk increasing mixing time increases the compressive strength of concrete 375 kg/cm2 in 28 days from the time the concrete mixing process increase the resistance of shows . Ash consumption in the non - crystalline silica , which is 88% of the project , has shown its high pozzolanic activity . Physical and chemical (XRF) examination showed that rice husk ash used in this project within the requirements of ASTM C-618 for pozzolan is located . XRD results show that the consumer is fully amorphous silica from rice husk ash . As the electro - microscopic pictures (sem) is observed in samples without Nano - silica and pozzolan rice husk , the concrete has uneven texture and large crystals are clearly visible which are connected with needle - shaped crystals and large pores are clear in concrete . However , the concrete samples with Nano - silica and rice husk pozzolan , concrete has a more amorphous structure which are homogeneous and integrated together . And the porosity of the concrete is significantly reduced , which increases the resistance of concrete.

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In this study, the effect of chaotic advection on laminar mixing is analyzed experimentally and numerically. Mixer includes two circular rotors and a circular stator in the way that rotational speed of each rotor could be controlled by time. This kind of mixer is widely used in the food and pharmaceutical industry. The performance of the mixer was investigated experimentally with dye injection and image recording. Moreover, the effect of chaotic flow on mixing numerically is studied qualitatively and quantitatively with Lagrangian fluid particle tracing, calculating the stretching rate of fluid elements and Poincare sections. The experimental results indicate that as a result of applying sinusoidal perturbation on rotational velocity of rotors, weak mixing zones will disappear with the passage of time, and fluid particles will be distributed uniformly in the surface of the mixer. Numerical simulation shows that the mixer flow is sensitive to initial condition when rotational velocity of rotors is variable, and this is one of important factors in chaotic flow. Further, calculation of stretching rate of fluid elements indicates that average exponential value of fluid elements stretching in the chaotic flow is two times more than non-chaotic one. This research, based on scientific concepts and theoretical application of chaos in fluid mechanics, denotes that the efficiency of low-speed mixers in highly viscous fluid mixing is increased without any increase in the consuming energy.

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In this article, the impact of external constant and uniform magnetic field is investigated on the mixing efficiency and also geometric and dynamic characteristics of two-dimensional isotropic MHD flow. For this purpose, the direct numerical simulation (DNS) is applied to two-dimensional incompressible magneto-hydrodynamic equations by pseudo-spectral method. Calculations show that external magnetic field causes deformation of vortexes and this deformation is increased by intensification of magnetic field. The dynamic characteristics of flow are affected by these deformations. Investigation of mixing efficiency shows that increase in magnitude of magnetic field or decrease in magnetic diffusivity coefficient causes mixing efficiency to reduce. For explore of the factors affecting on mixing reduction, small and large scale vortexes are studied. Investigation of external magnetic field effect on dissipated energy rate that is associated with changes in the dynamics of small vortexes shows that viscose dissipated energy rate is reduced in the presence of magnetic field compared to its absence. However results show that total dissipated energy rate is increased compared to no magnetic field presence. In order to demonstrate of large scale vertex dynamics, total kinematic and magnetic energy are considered. It is shown that in the presence of external magnetic field, energy is transferred from flow field to magnetic field due to Lorentz force that both leads to reduction of mixing efficiency.

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In this study, effects of zeta potential distribution and geometrical specifications are investigated on mixing efficiency in electroosmotic flows. Flow geometry in this research is a series of converging-diverging microchannels with different diverging ratios. Governing equations including the Navier Stokes equation for fluid flow and the Poisson-Boltzmann equation for internal electrical field are solved numerically in a two-dimensional domain by using the lattice Boltzmann method. Numerical simulations are validated against available analytic solutions for electroosmotic flow in homogeneous straight channels. The response surface methodology (RSM) is then employed to investigate relationship between flow variables and consequently to optimize mixing efficiency and flow rate of the channel. Results indicate that increasing the zeta potential ratio and diverging ratio, leads to increased value of flow rate, while meanwhile it decreases the mixing efficiency. Zeta potential pattern does not affect flow rate considerably, but its effects on mixing efficiency is noticeable. Furthermore, it is found that mixing efficiency and flow rate are more sensitive to zeta potential ratio than diverging ratio. At last, optimum parameters are determined by RSM which are 0.5 for zeta potential ratio, 0.6 for diverging height, and pp-nn pattern for zeta potential distribution, all associated to simultaneously maximized flow rate and mixing efficiency.

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The present study investigates the effect of the mixing chamber length on the effervescent atomizer internal two-phase flow and the liquid film thickness at the exit of the atomizer at different gas-to-liquid mass ratios. Therefore, the internal flow of this atomizer simulated for three different lengths of the mixing chamber, at the gas-to-liquid mass ratios of 0.08%, 0.32%, and 1.24% and at the liquid flow rate of 0.38 L / min by the volume of fluid interface following model. The simulation results show that the mixing chamber length does not have much effect on the dominant flow regime in the discharge passage. However, by increasing the mixing chamber length, the two-phase flow inside this chamber more expanded before entering into the discharge passage. Therefore, the two-phase interface instabilities in the discharge passage are lower for the atomizer with the longer mixing chamber. In addition, based on the measuring results of the liquid film thickness at the exit of the atomizer, the effect of the mixing chamber length on the thickness of this film depends on the gas-to-liquid mass ratio. Increasing the mixing chamber length at low gas-to-liquid mass ratio increases the liquid film thickness at the exit of the effervescent atomizer. While at high gas-to-liquid mass ratio, it's inverse. At middle gas-to-liquid mass ratio, the changes of the liquid film thickness at the exit of the atomizer with the mixing chamber length do not show a steady trend.