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This survey is dedicated to the study of Persian reactive tokens. Reactive tokens are short utterances such as “hmm”, “mm”, and alike, which are produced by the listener when he/she is listening. They do not require answers on the part of the speakers and they do not cause changing of the turn. Reactive tokens influence the success of the ongoing conversation. Their importance is understood in their absence. If they are used improperly, the conversation is disturbed. Without considering these tokens, we will ignore the important features of conversations. To our knowledge, no research has so far examined these token. In the corpus of this research, 960 tokens are transcribed in all the conversations, including face to face and telephone conversations, and studied in conversational analysis framework. Furthermore, super-segmental features and the degrees of reactive tokens’ influences are explored. The results showed that reactive tokens have different meaning in different context and we can consider a canonical and a non-canonical meaning for them. Also a spectrum for the degree of their influence is presented. The aim of this study is discovering the meanings and function of reactive tokens and some factors influencing their meaning in the conversations.

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In this paper, in order to detect the number of transmitting antenna in MIMO communication systems, it is proposed that the techniques such as AIC & MDL, which have been primarily designed so as to detect the number of Gaussian sources, are applied. Then a hypothesis testing based method for recognizing the type of modulation in MIMO communication systems with block orthogonal codes is suggested; in which in order to reduce the complexity of the traditional methods, simpler likelihood functions for testing hypotheses are applied. Furthermore, because in all modulation scheme detection methods, a proper estimation of channel gain (channel matrix) is required; in this paper, a new and efficient method based on SAGE iterative algorithm for estimation of channel matrix in MIMO communication system with space-time block codes is proposed. At the end of this paper, the performance and effectiveness of all proposed modules are separately and jointly analyzed by numerical simulations.

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Using of geomorphological flood studies including the recent advances in paleoflood hydrology are needed as a complement to conventional hydrological approaches. The factors effective on the Rais Kola watershed floods are divided into two categories: 1) drainage basin factors 2) river channel factors that are affected by lithology and tectonic and have played an important role on landform formation. To estimate the discharge through, paleostage indicator (PSI) and botanical methods several cross-sections of the studied channels on different reaches were used. Shear stress and stream power were estimated on the different reaches using HEC-RAS software. Then erosional effects and depositional forms generated by flood were investigated. The results showed that using paleostage and flow-competence could illustrate magnitude of flood in steep and small mountain rivers. The correct identification of flow processes is essential for proper design and accurate delineation of hazard zones.

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The purpose of this paper is to present a 2D depth-averaged model for simulating and examining unsteady flow patterns in open channel bends. In particular, this paper proposes a 2D depth-averaged model that takes into account the influence of the secondary flow phenomenon through calculation of the dispersion stresses. The dispersion terms which arose from the integration of the product of the discrepancy between the mean and the actual vertical velocity distribution were included in the momentum equations in order to take into account the effect of the secondary current. This model used a time-splitting method for solving advection, diffusion and other momentum equation terms. The proposed model uses an orthogonal curvilinear coordinate system efficiently and accurately to simulate the flow field with irregular boundaries; it also used a finite volume projection method approach for solving the governing equation in a staggered grid. Two sets of experimental data were used to demonstrate the model's capabilities. The comparison of the simulated water surface elevation with the measurements shows good agreement and indicates that inclusion of the dispersion terms improved the simulation results.

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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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Monetary conditions index (MCI) is used as an intermediate target of monetary policy in many developed countries. More recently, monetary authorities in some developing countries have also attempted to use this operational target to determine the stance of monetary policy in their countries. The MCI is usually computed as a weighted sum of changes in interest rate and exchange rate. The use of interest rate in constructing MCI might not be appropriate in developing countries due to the lack of efficient financial markets in these countries. Some authors have emphasized on the role of credit channel in monetary transmission mechanism for developing countries. Using weighted sum of profit rate, exchange rate and banks credit, this paper constructs proper MCI for the Iranian economy. Aggregate demand and price equations are used to estimate the weights. Finally, the forecasting power of these indices using non-nested tests and root mean square errors is compared. The results show that the MCI augmented with banks credit has better predicting power than those without credit channel. Moreover, it is also revealed that real MCI, as an intermediate target, is preferred to nominal ones.

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ABSTRACT A numerical investigation of mixed convection heat transfer with nanofluid and pure water from a heat source in a horizontal channel is performed. The walls of the channel are adiabatic and the heat source is placed at the bottom wall of the channel. Free flow at cold temperature enters channel and takes heat from heat source. Discretization of the continuity, momentums and energy equations are achieved through a finite volume method and solved with SIMPLE method. The Brownian motion of nanoparticles is simulated to determine the thermal conductivity of the nanofluid.The results show that using the nanofluid caused to heat diffusion and average temperature of source to increase. Also, increase in solid volume fraction causes increase in heat transfer especially at high Reynolds number. It is understand that with increase in ratio of length to height of source in its constant area, heat transfer decreases first and then increases.

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In this paper the effects of the inlet fluid temperature on the electro-osmotic flow pattern in a two-dimensional microchannel with constant walls temperature is investigated with solving the governing equations by the Lattice Boltzmann method. The main objective of this research is to study the effects of temperature variations on the distribution of ions and consequently internal electric potential and velocity field. For make possible to use the Boltzmann ion distribution equation, cup mean temperature for every cross section of the microchannel is used. At the used Lattice Boltzmann method, LBGK model for modeling the Boltzmann collision function and the Zou-He boundary conditions method for velocity field has been used. Wang model for solving the Poisson-Boltzmann and He-Chen model for solving the energy equation has been used. The results show that, with increase the temperature difference between the inlet flow and the walls, the electro-osmotic flow rate increases. Also, observed that with decrease the external electric potential and the electric double layer thickness and increase the temperature difference at the inlet zone of the microchannel, a region with return flow is formed which can be used for controlling the internal flow pattern.

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This paper presents a gain scheduled autopilot for pitch channel of a flying vehicle. The selected method is based on polynomial fuzzy systems. The method does not involve linearization about operating point. First the polynomial fuzzy model of pitch channel of the flight body is derived. Next, using polynomial fuzzy system methodology the controller is design such that the outputs of the nonlinear plant drive to follow those of a stable reference model. Because of avoiding actuator saturation, some constraints derived that guarantees the amplitude of control signals be less than a specific threshold. It is considered that the controller has a known structure like three-loop autopilot. In other words the three-loop fuzzy polynomial autopilot is design to satisfy stability and performance of the closed loop system over a wide range of parameter variation. Stability and performance conditions derived in terms of sum of square will solve numerically via SOSTOOLS.
 
 

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In this study, the geometrical changes at cathode electrode in proton exchange membrane (PEM) fuel cell has been considered by inserting baffle plates across the channel. The effects of the blockage with various gap ratios, shape, thickness and numbers of the baffle plates, and the porosity of the diffusion layer on the oxygen transport and the pressure drop across the channel length are explored. It is revealed that partially blocked oxygen channel with rectangular baffle has the most velocity and oxygen concentration in the gas diffusion layer/catalyst layer interface than that of the other shape of plates; however results in a penalty of high pressure-loss. Increasing the porosity of gas diffusion layer (GDL), baffle plate thickness and baffle number and/or reducing the gap size in order to enhance the reactant gas transport result in pressure loss. Here, among the parameters considered, the porosity of GDL, gap ratio and plate number have the most remarkable impact on the oxygen transport to GDL and variation in pressure drop.

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Flow analysis in the microchannels has recently accelerated dramatically. In this paper, numerical investigation of Joule heating effects on the electroosmotic flow through a microchannel with the trapezoidal cross-section and constant wall temperature have been presented. The energy equation for the temperature distribution, Navier–Stokes equation for the velocity distribution and a Poisson equation for the electric potential distribution have been solved by using the finite-volume method in a system curvilinear coordinates. Thermophysical properties such as the dynamic viscosity and electric conductivity vary with temperature. Results show that by increasing the Joule number, the temperature, velocity and mass flow rate increase with constant EDL number. Without considering the Joule heating effects, the increments of EDL number causes in the mass flow rate to increase, but with considering the joule heating effects, the increasing of mass flow rate continues until EDL number 15 and after that the flow rate decreases. On the other hand, when the cross-section is reduced by the increasing aspect ratio, the joule number remains constant while the mean temperature decreases.

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Multi-channels Electroencephaloram (EEG) needs a long preparation time for electrode installation. Furthermore, using a large number of EEG channels may contain redundant and noisy signals which may deteriorate the performance of the system. Therefore, channels reduction is a necessary step to save preparation time, enhance the user convenience and retain high performance for an EEG-based system. In this study, we present a simple and practical EEG-based emotion recognition system by optimizing the channels number based on two different Common Spatial Pattern (CSP) channel reduction methods. We applied feature extraction based on the Fast Fourier Transform (FFT) algorithm and classification method based on the Support Vector Machine (SVM) and K-nearest neighbor (KNN) which make our proposed system an efficient and easy-to-setup emotion recognition system. According to experimental results, the proposed system using small number of channels not only does not increase the error of the system, but also improves the performance of the system compared to the use of total number of channels.    

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In the present paper, Molecular Dynamics Simulation (MDS) is performed for Poiseuille flow of liquid Argon in a nanochannel by embedding the fluid particles in an external force with different potential functions. Three types of Lennard-Jones (LJ) potentials are used as interatomistic or molecular models for evaluations of interactions and density, velocity profiles across the channel are investigated. The interatomic potentials are LJ 12-6 potential, LJ 9-6 potential and LJ-Smooth potential. Density and velocity profiles across the channel are investigated. Obtained results show that hydrodynamic characteristics and behavior of flow depends on the type of interaction potential. It is shown that the LJ 9-6 predictions for velocity and temperature are larger than those of LJ12-6 and LJ-Smooth potentials. Also, applying LJ 9-6 results in further calculations time. The results show the effect of interaction force model on the understanding and analyzing of nanoscale flows.

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Abstract- Hydrodynamics and Heat transfer of a gaseous flow in microchannels is performed numerically. Velocity and temperature at the channel inlet is uniform and the rarefaction effect is imposed to the problem via velocity slip and temperature jump boundary conditions, according to the slip flow regime. The channel is sufficiently long to reach fully developed flow at the outlet. The numerical methodology is based on the control volume finite difference scheme and discrete equations are solved using SIMPLE algorithm. Effects of various parameters such as viscous dissipation, rarefaction, axial conduction and thermal creep on heat transfer have been considered. The results indicate that the Nusselt number in microchannels has a different value than in conventional channels. Local Nu number is found to experience a jump by the presence of viscous dissipation. The magnitude of the jump is independ of the Brinkman number values. Heat transfer is affected in two opposite directions by rarefaction increasing. Also, as Peclet number increases, there is a weak increase in fully developed Nu number values but there is significant effect of Kn number on it.

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Diversity, accessibility and reliability are the three main factors governing the adoption of information sources by farmers in rural areas. Based on the research hypothesis, the existing knowledge and information delivery system in the agricultural sector, functions far below the ever changing nature and tangible needs of existing farming systems. The main objective in this study is to determine and prioritize farmers’ information channels and their communication networks within rural areas of 19 townships of Isfahan Province – the central part of Iran. After exploratory field visits of several villages, a questionnaire was designed and pre-tested for its validity and reliability (Alpha= 82%). The statistical society included all farmers who had regular contacts with the local extension offices. The sample population was 228 farmers who were selected through a two-step random sampling method from the villages with an extension office. The results showed that extension system disregarded farmers’ local media and did not meet their actual needs. The extension system failed to build trust among the local communities. Moreover, farmers’ trust in one information source had a synergic effect on the others. The sources were categorized in three groups based on the farmers’ preferences. The printed materials did not play any significant role in the knowledge and information processes. There was also a significant correlation between dependent variables (determination of information source by farmers) and the independent variables (for example: farming land size and farmers educational level). Finally, most farmers claimed that visiting ‘local extension service offices’ was mainly in response to their urgent needs to acquire subsidized agricultural input such as fertilizer, rather than acquisition of information and were yet disappointed.

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Abstract- Mixed convection flow of a water-copper nanofluid in a channel under magnetic field effects has been numerically investigated. The fluid flow and temperature fields as well as the heat transfer rate have been determined by solving the Navier-Stocks and energy equations. In this study, the effects of various parameters such as the Richardson number, the Hartmann number, the solid volume fraction and the channel angle on the thermal performance of the channel have been examined. The results showed that at high Richardson numbers, the heat transfer rate decreased as the Hartman number increased. It was also found that the heat transfer rate increased as the Richardson number, the solid volume fraction and the channel angle increased. The maximum flow reversal was observed to occur in a vertical channel.

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In this paper, heat transfer in a sinusoidal channel filled with nanofluid under magnetic field effect is investigated numerically. The magnetic field transversely applied to the channel. Water as a base fluid and copper as nano particles were considered .The Maxwell-Garnetts model and Brinkman model for heat conduction coefficient and dynamic viscosity were used respectively. The effects of changing some parameters such as shape ,volume fraction , Hartmann number and Reynods number were considered. The results show that increasing in all mentioned parameters lead to increasing in Nusselt number. Volume fraction is mainly affect on maximum local Nusselt number in each channel’s wave while Hartmann number is affected minimum and maximum Nusselt number.

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One of the fundamental problems of Electrical Discharge Machining (EDM) process is tool electrode wear. In this study, ultra fine grains (UFG) structure of pure copper was used to improve performance and also increase the electrical wear resistance of tool electrode. Equal Channel Angular Pressing (ECAP) was used to reduce the crystal size of pure copper. Samples were processed through ECAP die up to 8 passes, and then used as electrode in EDM process. The effect of electrodes grain size, discharge current, and machining time on the metal removal of the work piece and electrical wear of the electrodes were investigated. In addition, the microstructure, and electrical conductivity of copper tool electrodes were examined. By applying the ECAP on pure copper a fine, approximately 50-200 nm grain size, microstructure was obtained after 8 passes. The results show that for finer crystalline structure of copper electrodes, electrical wear decreases but material removal rate is somehow constant.

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In this paper, the effect of gas and liquid inlet superficial velocities and distance from upstream on slug frequency is studied experimentally. Empirical correlations are also presented based on the obtained results. The tests are conducted for liquid holdup αl= 0.75 and three distances from inlet in a long horizontal channel made of Plexiglas with dimensions of 510 cm2 and 36m length in Multiphase Flow Lab. of Tarbiat Modares University. The superficial liquid and air velocities rated as to 0.11-0.56 m/s and 1.88-13 m/s, respectively. The obtained results show that slug frequency is dependent to superficial liquid velocity directly. Slug frequency decreases with slip ratio increase. Slug frequency has strong dependency on superficial liquid velocity and increases monotonically with it. However, superficial gas velocity has damping effect on slug frequency. As slug moves towards downstream, slug frequency will be decreased but slug velocity will be increased.