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Considering the main role of listening comprehension in second language learning, it seems that providing listening strategies to language learners is necessary. New technologies are used to facilitate learning and podcast is one of the new tools used in language teaching today. The purpose of this descriptive-analytical study is to investigate whether metacognitive training with the help of podcasts can be used as an effective tool in enhancing listening comprehension. The research problem is caused by the lack of sufficient knowledge of language learners about metacognitive strategies, and in this regard, the role of the teacher in teaching these strategies is very important. This study can help French language teachers to include metacognitive strategies in improving listening skills and conventional methods. Revise yourself. For this purpose, 30 language learners were divided into two experimental and control groups based on the pre-test results. The experimental group received the podcasts through Vandergrift's metacognitive training, while the control group was taught the podcasts without any additional instructions or strategies. The results with the help of note taking, self-assessment questionnaire, direct observation and using spss software (t-test) showed that the metacognitive strategy has a positive effect on students' listening comprehension.

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From 2009 to 2012, 16 species of Curculionidae (Coleoptera) from the subfamily Lixinae were collected on 17 species of food plants in Iranian rangelands. Identified species belong to seven genera in the tribes Lixini and Cleonini. The host plants from which they were collected were in the families Asteraceae, Fabaceae, Apiaceae, Campanulaceae, Brassicaceae and Zygophyllaceae. Of the 16 species that we captured, two (Lixus subfarinosus Desbrochers, 1893 and Larinus remissus Faust, 1889) represent the first records from Iran. These new data also extend the known ranges of several species (Larinus fucatus Faust, 1894, Larinus grisescens Gyllenhal, 1835, Microlarinus rhinocylloides Hochhuth, 1847 and Bangasternus planifrons (Brulle, 1832) in Iran. The distribution of beetles and their associated host plants are presented and ecological notes on each species are provided.

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Piarom is considered as one of the most important semi-dried date fruits in Iran which has been highly affected by stored pests. The current study was aimed to evaluate the effects of the modified atmosphere packaging (MAP) and vacuum packaging (VAP) methods on storage pests control and date quality. To do so, Piarom variety were packaged in two package systems, including passive modified atmosphere and vacuum package system. The control samples were kept unpackaged. The packages were kept under two different storage conditions; at 4 °C and 55 ± 10% RH, and 25-27 °C and 70 ± 5% RH for 30, 60, 90 and 150 days. The experiment was carried out based on a completely randomized design arranged in factorial with four replicates. The results showed that Indian meal moth Plodia interpunctella (Hübner)and sawtoothed grain beetle Oryzaephilus surinamensis (L.) are the most important storage pests with 87.5 and 12.5% contamination, respectively. The passive MAP and VAP reduced the pests infestation rate significantly compared to control. Also, they could better preserve pH (5.88 and 5.85 for MAP and VAP, respectively) than the control (5.78). Changes in water activity in MAP and VAP were almost the same at the two storage conditions i.e., ambient and at 4 °C and was significantly different from the control. The maximum water activity change was observed in control treatment.

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 In this study, a new simple method for design and implementation of rectangular waveguide leaky wave antenna with the longitudinal long slot is presented. In this method which has been done using HFSS, firstly, the waveguide attenuation is calculated based on the position of the slot in relation to the waveguide broad wall. Then the desired aperture illumination is fitted to the slot position on the broad wall of the waveguide by MATLAB. Finally, a Taylor-distributed rectangular waveguide leaky wave antenna with 30 dB SLL designed and fabricated in ku band. The good agreement between the simulation and the measurement results for radiated patterns verifies the effectiveness of the presented method.
 

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This Study presents a numerical investigation of the hydro-thermal behavior of a Non-Newtonian ferrofluid (non-Newtonian base fluid and 4% Vol. Fe3O4) in a rectangular vertical duct in the presence of different magnetic fields, using two-phase mixture model, power-law model, and control volume technique. Considering the electrical conductivity of the base fluid, in addition to the ferrohydrodynamics principles, the magnetohydrodynamics principles have also been taken into account. To study the effects of non-Newtonian base fluid using power-law model, assuming the same flow consistency index with viscosity of Newtonian fluid, two different power law indexes (i.e., n=0.8 and 0.6), have been investigated and the results have been compared with that of Newtonian ones (i.e., n=1). Three cases for magnetic field have been considered to study mixed convection of the ferrofluid: non-uniform axial field, uniform transverse field and another case when both fields are applied simultaneously. The results indicate that the overall influence of magnetic fields on Nusselt number and friction factor is similar to the Newtonian case, although, by decreasing the power law index, the effect of axial field on velocity profile, Nusselt number and friction factor become more significant. Moreover, the results indicate that electrical conductivity has a significant effect on the behavior of ferrofluid and cannot be neglected and also negative gradient axial field and uniform transverse field act similarly and enhance both the Nusselt number and the friction factor, while positive gradient axial field decreases them.

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In order to power and hydrogen production, combination of Matiant cycle with an ORC cycle and PEM electrolysis have been analyzed from the viewpoint of energy and exergy. Waste heat of the Matiant cycle is used to run the ORC cycle. Effect of some decision variables i.e. evaporator temperature, minimum temperature difference in heat exchanger, degree of superheating in ORC turbine inlet and isentropic efficiency of ORC turbine on the rate of produced hydrogen, ORC produced power and exergy efficiency of the combined system have investigated. It is observed that, increasing minimum temperature difference leads to decrease in the rate of produced hydrogen, ORC produced power and consequently exergy efficiency of the combined system. Also change in the evaporator temperature makes an optimum value of rate of produced hydrogen, ORC produced power and therefore the exergy efficiency of the combined system. It is obtained that, rising the degree of superheating in the ORC turbine inlet decreases the rate of produced hydrogen, ORC produced power and the exergy efficiency of the combined system. As it was expected, increasing isentropic efficiency of ORC turbine leads to an increase in rate of produced hydrogen, ORC produced power and therefore the exergy efficiency of the combined system.

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In this article, the free and forced convectional heat transfer in a rectangular porous fin with considering pressure loss across the fin length is investigated analytically. A well-known Differential transformation method is employed to obtain the solution of energy balance equation. Convergence of obtained solution is examined by previous works and they are found to be in a good agreement. In order to simulate heat transfer through porous media, Darcy model is applied. Also convective heat transfer coefficient is assumed to be constant. Dimensionless temperature distribution is defined as a function of convection and porosity parameters. Also the effects of pressure loss across the fin length on the temperature distribution, rate of heat transfer, fin efficiency and effectiveness of fin are studied. A comparative study is also made between the porous and solid fins for an equal mass of fins. It is highlighted that the porous fin transfer always more heat at specific condition compared to the solid fin. Results show that all of thermal parameters are influenced by pressure loss parameter. So in order to reach to high fin efficiency, pressure loss across the fin length should be controlled.

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In this paper, ferrofluid flow in a closed cooling loop without any mechanical pump has been simulated. The flow of the ferrofluid in the closed loop is resulted from applying a non-uniform magnetic field and the thermo-magnetic effect of the ferrofluids. The ferrofluid consist water and different volume fractions of iron oxide nanoparticles with nanoparticle diameter of 13nm. The two phase mixture model and the control volume technique have been used in the present study. The applied non-uniform magnetic field is resulted from an electromagnetic solenoid and the steady and also the transient modeling of the flow in the cooling loop from start point (stagnant ferrofluid in loop) have been carried out. The obtained results show that by applying magnetic field and also by taking advantage of temperature dependent property of the magnetic susceptibility, a flow of ferrofluid is created in the loop and by increasing the heat input (heater power) in the loop, the flow rate in the loop is increased. Moreover, the results show that by having a cold source (for rejection of produced heat) with higher constant temperature, the flow rate in the loop increases. Furthermore, the flow rate in the cooling loop is increased as the volume fraction of the nanoparticles in the base fluid increases. The mentioned cooling loop can be used in the electronic cooling systems.

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Despite the unique usage of electrical discharge machining process at machining in small dimensions, machining complex shapes and machining of high-strength parts such as ceramics and heat treated steels, which can’t be machined by traditional machining methods, low machined surface integrity achieved by electrical discharge machining process is one of the most important limitations of this process. In this investigation the machined surface integrity will be improved by applying ultrasonic vibrations to tool electrode and external magnetic field around gap distance of electrical discharge machining process, simultaneously. So several experiments were designed and performed based on full factorial method by selecting pulse current and pulse duration as the most important input parameters, in order to study the effects of pulse current and duration on surface integrity of workpiec machined by this hybrid process and to investigate the effects of tools ultrasonic vibrations and external magnetic field on machined surface roughness and integrity of machined surface. According the results, machined surfaces roughness is increased by applying ultrasonic vibrations to tool electrode and external magnetic field around gap distance of electrical discharge machining process, simultaneously, while the SEM pictures of machined surfaces showed that the, amount of created surface cracks, blowholes, globules and beads of debris are decreased and integrity of machined surfaces by EDM process is improved by applying ultrasonic vibrations to tool electrode and external magnetic field around gap distance, simultaneously.

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In this study, the analysis of heat transfer in porous fin considering thermal radiation and natural convection is investigated. In order to model radiation, discrete ordinates method is used. Also, Darcy–Brinkman–Forchheimer model is applied for simulating porous media. A Least square method and numerical simulation (computational fluid dynamics) are applied to obtain the solution of governing equations. In addition, accuracy of LSM results is compared with the numerical simulation results. Moreover, the effects of homogeneous and non-homogeneous porosity along the porous media, Rayleigh number, Darcy number, porosity, surface emissivity, on temperature distribution along the length of porous fin and Nusselt number are investigated. Results show that the numerical simulation and LSM results are in good agreement with each other (With average error of 3.39%). Also neglecting thermal radiation effect in heat transfer analysis of porous fin leads to 10- 20% error in the Nusselt number value. Moreover, by applying nonlinear variable porosity along the porous media, the Nusselt number will increase up to 23% with respect to the homogeneous porosity. So in order to enhance heat transfer rate, porosity profile should be applied appropriately along the porous media.

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In this paper, a robust discrete control law is presented, using a time delay control method for an omnidirectional mobile robot in the presence of system uncertainties. Although time delay control method has attracted the great attention of researchers due to its structure simplicity, the major part of these research have been performed by the assumption of continuous time delay control and infinitesimal time delay that is in contradict of physical nature of digital devices, as implementation tools of time delay controllers, which have finite and specific sample time. Also, the discretization of continuous-time systems has been usually done by Euler estimation method, which has sufficient accuracy for infinitesimal sample times. So, in this paper, after modeling the robot, considering the dynamics of robot motors, a new method for more accurate discretization of continuous nonlinear systems is presented and, then, a robust discrete control law is designed, using the backstepping technique at the voltage level of the robot motors. In the design of control law, a new adaptive sliding mode method is used to overcome the system uncertainties and stability of the closed-loop system is proved by error convergence to a small neighborhood of zero. The proposed controller is designed in the discrete domain without the necessity of being known the bound of system uncertainties and simulation results represent the desired performance of the controller in trajectory tracking.
 

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The aim of the current research was to investigate the hot tensile behavior and fracture morphology of 410 steel in the temperature range of 950-1100°C and two strain rates of 0.05 s^-1 and 0.5 s^-1. The results showed that the peak stress and yield stress decreased with increasing temperature, which confirmed the decrease of strength against deformation with increasing process temperature. In strain rate of 0.05 s^-1 with increasing temperature, the peak strain decreased continuously, while in strain rate of 0.5 s^-1 was observed an increment trend after initial decrease due to competition between work hardening and softening mechanism such as dynamic recovery and dynamic recrystallization. The fracture morphology results showed that they were in good agreement with the mechanical results when at 950 °C the brittle fracture mechanism had a high contribution and the soft fracture surface morphology (increasing dimples and decreasing cleavage planes) was dominant with increasing process temperature. At strain rate of 0.05 s^-1, the size of the voids and cracks formed during process was much larger than the cracks created at strain rate of 0.5 s^-1, which indicated considerable tearing and decrease in fracture strain (elongation) of the samples in during hot tensile testing at low strain rate.

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