Showing 17 results for Pouyan
Volume 10, Issue 2 (Spring 2022)
Abstract
Aims: This study has been done to investigate the hydrogeological drought and groundwater quality changes over the time in Semnan and Damghan plains.
Materials & Methods: In this research, the groundwater level and groundwater quality changes in of these plains has been evaluated using monthly piezometric wells data for April as groundwater-recharging month and October as groundwater-discharging month and six groundwater quality factors including pH, Chloride (Cl-), Total Dissolved Solids (TDS), Electrical Conductivity (EC), Calcium (Ca2+) and Magnesium (Mg2+) were considered to determine groundwater quality changes. Groundwater Resource Index (GRI) and Groundwater Quality Index (GQI) were used to determine hydrogeological drought and changes in its quality, respectively, in studied plains from 2004 to 2018.
Findings: The results illustrated that the trends of groundwater level and GRI are decreasing and there is no steady trend for these indices over the studied period and GRI value is totally higher in city surrounding regions in both plains. According to results of GQI, EC and TDS factors have the highest effect on the groundwater quality, respectively, compared to other factors. GQI value is higher in central and northern parts than compared to other parts in Semnan plain, while in Damghan plain, GQI value in central and western parts is higher than eastern parts.
Conclusion: The correlation between GRI and GQI showed positive results in both plain with 0.542 in Semnan and 0.672 in Damghan, which reflects that the groundwater quality changes with groundwater level changes
Volume 10, Issue 4 (Fall 2022)
Abstract
Aims: In the present study, groundwater quality evaluation for drinking and irrigation purposes in Tashk-Bakhtegan and Maharloo basin was investigated using the data from 420 observation wells.
Materials and Methods: To assess the suitability of groundwater in terms of hydrogeochemical parameters including potassium (K+), sodium (Na+), magnesium (Mg2+), calcium (Ca2+), chloride (Cl-), bicarbonate (HCO3-), sulfate (SO42-), Electrical conductivity (EC) and total soluble solids (TDS) for 420 monitoring wells in November 2017 (as a dry month) and May 2018 (as a wet month) and to calculate the Drinking Water Quality Index (DWQI) and Irrigation Water Quality Index (IWQI) were used.
Findings: The results showed that groundwater quality for drinking purpose varied widely across the basin, with the average DWQI value increasing from 238.83 in November 2017 to 249.79 in May 2018. IWQI results also indicated that in most areas, especially in the northern and southern parts of the basin, groundwater has moderate, high and severe limitations for agricultural activities in both months. The average value of IWQI increased from 47.67 in November, 2017 to 49.67 in May, 2018, indicating a slight increase in groundwater quality for agricultural use.
Conclusion: According to the obtained results, necessary precautions should be taken for groundwater before using it for different purposes, and the results of this study can be used in the planning and management of groundwater resources.
Volume 12, Issue 1 (Spring & Summer 2008)
Abstract
The present Research has surveyed the foreign policy of the Islamic Republic of Iran vis-à-vis the Republic of Azerbaijan. Based on some of the most important geographical and geopolitical realities that exist between the two states, by presenting one main question and two hypotheses, used as guide into a thorough geopolitical assessment of the issue. Based on the findings, we come to this conclusion that the none-cordial disposition of the Republic of Azerbaijan towards Iran, and some of the uncharted pasturings and unspecified strategies by the Islamic Republic of Iran render ineffective so many positively positoned areas of common geographical and/or geopolitical interests such as territorial contiguity, common religious tendency (both Shiite), common ethnicity, common economic interests (agricultural and irrigation possibilities), common cultural and historical backgrounds. Unfortunately, the continued policies between the two states have further made all these possibilities to render ineffective. The main outcome of the research shows that some of the issue are resultant from a suspected nationalistic disposition on the part of the Iranians; and similarly, a persistent attitude of none cordiality from the Azeris. Moreover, the Republic of Azerbaijan has yet to present a logical and pragmatic reason to explain its negative diplomatic strategy against the Islamic Republic of Iran
That could justify its distrustful policy towards iran.
The research consequently has proposed the following general aims and strategies to be implemented in Iran’s faring policy towards the Republic of Azerbaijan:
General aim: the faring policy of the Islamic Republic of Iran in relation to the Republic of Azerbaijan is determined by geographical and geopolitical realities that exist between the two states.
Strategy: to develop mutual relations based on the need for neighborly dispositions, to understand the geopolitical dictates of time and space, common national interests and aims,economic cooperation,and to explore other avenues that would develop mutual trust in order to broaden cooperation between the two states.
Volume 12, Issue 2 (Spring 2024)
Abstract
Aims: This study aims to assess the variations in the trend of drought using indices in Northwest Iran as vegetative cover plays a vital role in environmental stability.
Materials & methods: To achieve this goal, the study includes three stages: determining the Standardized Precipitation Evapotranspiration Index (SPEI) using monthly temperature and precipitation data from meteorological stations, calculating the Vegetation Health Index (VHI) based on derived datasets from MODIS satellite images for the period 2001-2021, and examining the correlation between indices to determine the duration of vegetation cover response to water scarcity and identify trends at 3, 6, 9, and 12-month time scales.
Findings: Based on the results of the Mann-Kendall test, the stable (48.56%) and increasing (50.43%) trends cover most of the studied areas and a smaller area had a decreasing trend (1.01%) trend. Additionally, positive correlations between VHI and SPEI were observed across all time scales. The SPEI-3 months showed the highest Pearson correlation (R2= 0.83) with VHI values for the growing season, indicating that water accumulation in the past 3 months had the greatest impact on vegetation cover.
Conclusion: This study, while emphasizing the necessity of monitoring and managing drought, with a focus on vegetation cover status in Northwest Iran, especially in East Azerbaijan province, introduces drought indices as a crucial component of the drought monitoring system.
Volume 14, Issue 2 (5-2014)
Abstract
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 510 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.
Volume 14, Issue 3 (6-2014)
Abstract
Abstract- In this paper, the effect of gas and liquid inlet velocities and for the first time the effect of liquid hold up on slug initiation position are studied experimentally. Empirical correlations are also presented based on the obtained results. The tests are conducted for three liquid hold ups (0.25, 0.50 and 0.75) in a long horizontal channel made of Plexiglas with dimensions of 510 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 as αl=0.25, slug initiation position is increasing monotonically with Usl and Usg. During αl=0.50, slug initiation position is increasing with Usl and Usg but the slope is smoother than αl=0.25. For αl=0.75, slug initiation position is decreasing monotonically with Usl and Usg. In the case of equal void fraction of phases, slugs are generated weakly (low pressure). However, for the unequal void fraction of phases strong slugs (high pressure) are formed.
Volume 14, Issue 7 (10-2014)
Abstract
In this article, two-phase slug flow is simulated numerically in a horizontal duct with rectangular cross-section using Volume Of Fluid (VOF) method. Conservation equations of mass, momentum and advection equation are solved in open source OpenFOAM code accompanying k-ω SST turbulence equations. Simulation is conducted based on the experimental results in the duct with rectangular cross-section. The results shows, due to Kelvin-Helmholtz (K-H) instability criteria slug initiation forms in the air-water interface during three dimensional turbulence modeling. Water level was increased slightly at interface in both numerical simulation and experiment. This level increase satisfies the K-H instability to generate a slug at interface. During slug initiation, the pressure behind slug is increased significantly. Big pressure gradient at the beginning of the slug in compare to the end of it causes the slug length to be increased as propagate along the duct. The numerical simulation of present research is capable of predicting the slug length accurately in accordance with experiment; however, the slug position with 22% inaccuracy was obtained. Comparison of the results with the numerical and experimental results of other researchers confirms higher accuracy of flow prediction in the present work.
Volume 14, Issue 11 (2-2015)
Abstract
In the present article, velocity and deformation of an air bubble have been considered in quiescent liquid at different consecutive slopes from 5 to 90 degrees in respect to horizontal condition. To establish these purposes, air-water two-phase flow has been simulated numerically by using volume of fluid method. The two-phase flow interface has been traced by using Piecewise Linear Interface Calculation (PLIC) method. Surface tension force was estimated by Continuum Surface Force (CSF) model. The simulation results show that maximum bubble velocity occurred at 45 degrees which is in agreement with the previous researchers result. Simulation of bubble movement was also continued to two consecutive slopes at different angles. At slope deviation location, a vortex was generated due to liquid movement governed by gravity forces. This vortex changes the bubble velocity as well as bubble shape. This vortex also reduces the bubble velocity and changes the bubble nose shape from sharp to flatten at deviation from low to high slope values. However, at deviations from high to low slope values, the bubble nose becomes more sharpened in addition to bubble velocity increase. The maximum average velocity of bubble movement at two consecutive slopes was obtained during the condition that the first and second slopes were set to 60 and 30 degrees, respectively.
Volume 15, Issue 6 (8-2015)
Abstract
In this paper, natural convective heat transfer of nanofluids in a uniform magnetic field between the square cavity and inner cylinder, was simulated via Lattice Boltzmann Method. The inner cylinder in square shape, diamond, and circular has been examined. Square cavity walls and inner cylinder surfaces are at a constant cold and warm temperature, respectively. The flow, temperature, and magnetic field is calculated with solving flow, temperature, and magnetic distribution functions simultaneously. D2Q9 lattice arrangement for each distribution function is used. The results clearly show the behavior of fluid flow and heat transfer between the cavity and the cylinder. The results have been validated with available valid results showing relatively good agreement. The effects of Rayleigh number, Hartmann number, void fraction and type of nanoparticles on natural convective heat transfer are investigated. This study shows that for all three geometries used with the same void fraction, type of nanofluid, and Rayleigh number, natural convective heat transfer decreases with Hartmann number. Also, when Hartmann number was had fixed, natural convective heat transferwas increased with Rayleigh number. Thus, to select the right geometry for optimum natural convective heat transfer, our needs to pay special attention to Hartmann and Rayleigh numbers. In addition, viod fraction and type of nanofulid can affect heat transfer directly.
Volume 15, Issue 13 (Special Issue 2016)
Abstract
Volume 16, Issue 4 (6-2016)
Abstract
The aim of this paper was to study the thermophoresis effect on the deposition of nano-particles from diesel engine exhaust after the dilution tunnel using a computational modeling approach. Dilution tunnel was used in order to dilute the exhaust gas to the extend that was suitable for the measurement systems. The Lagrangian particle tracking method was used to model the dispersion and deposition of nano-particles. For the range of studied particle diameters (from 5 to 500 nm), the Brownian, thermophoresis, gravity and Saffman Lift forces are considered. After verifying the code, the importance of different forces was evaluated. Due to the temperature gradient between the exhaust gas and the pipe walls, particular attention was given to include the thermophoresis force in addition to the other forces acting on nano-particles. The results showed that for the range of nano-particle diameters studied, the Brownian force was the dominant force for particle deposition. Furthermore, the thermophoresis force was important even for relatively low temperature gradient and cannot be ignorable especially for larger particles. The maximum thermophoresis effect occurred for 100 nm particles. The gravity had negligible effects on nano-particle deposition and can be ignorable for particles with diameter less than 500 nm. The Saffman lift also had negligible effects and its effect was noticeable only for the deposition of 500 nm particles. The results of this paper could provide an understanding of two-phase flow emission from diesel engines especially after the dilution tunnel.
Volume 17, Issue 2 (Summer 2017 2017)
Abstract
National accounts data are of the most important statistical tools in planning and making economic policy. Therefore, forecasting the main economic variables in the economy is of great importance. Economic growth is one of the key macroeconomic variables, which gets top priority in forecasting. The purpose of this study is to identify the appropriate methodology for forecasting economic growth in Iran. This study introduces fuzzy regression model and its’ ability to forecast economic growth of Iran in comparison with Error Correction Model (ECM). To do this, the Iran’s GDP is modeled through ECM and Fuzzy regression models using annual data form 1959 to 2001. Then, Iran’s GDP growth is predicted for 2002-2012. Finally, the performances of these models are compared using common criteria for evaluating forecast accuracy including mean absolute error (MAE), root mean square Error (RMSE), mean absolute percentage error (MAPE) and Theil’s inequality coefficient (TIC). The results indicate that the performance of fuzzy regression is far better than that of ECM in predicting GDP growth in Iran. Moreover, forecast accuracy of fuzzy regression model is of statistically significant difference in comparison with ECM model.
Tayebe Shahi, Seid Mahdi Jafari, Morteza Mohammadi, Mohsen Pouyan, Mahdi Ebrahimi, Sareh Hoseini,
Volume 17, Issue 107 (January 2021)
Abstract
abstract
Natural vinegar is produced from two stages of alcoholic fermentation by yeasts and acid fermentation by acetic acid bacteria. The most important effective factors in vinegar production process are availability of nutrients and yeast content for faster and higher rate of fermentation processes. This study was carried out to evaluate the effect of yeast level (0, 2 and 4%) and glucose concentration (0 and 10%) on parameters including acidity, pH, brix, phenolic compounds and antioxidant properties of jujube vinegar. For this purpose, washed jujubes were exposed to different concentrations of glucose and yeast. Then the samples were kept for 45 days at 45 ° C to produce vinegar. Our results showed that there was a direct correlation between the increase of yeast and glucose content with acidity, brix, phenolic compounds, antioxidant properties and pH reduction; the amount of yeast was more effective than glucose. Also, we found that pH and acidity were between 3.00-3.46 and 1.39-3.51, respectively. A good correlation was observed between total phenolic content and antioxidant activity. The minimum and maximum phenolic compounds and antioxidant properties were 3582.8 mg / L and 33.87%, 6403.3 mg / L and 45.37%, respectively which was obtained with 2% yeast and 0% glucose, and 4% yeast and 10% glucose. Obtained results indicated that yeast increases the antioxidant property and reduces vinegar production time to 35 days in 4% yeast than 2% and 0%, which is an important economic factor in the production of vinegar.
Volume 18, Issue 4 (11-2018)
Abstract
In this paper, for the first time using of Bayesian regularized artificial neural network (BRANN) model, which is a novel method of among soft computing (SC) methods (such as fuzzy logic, genetic programming, neural network) to predict the rotational capacity of wide-flange steel beams. Steel is one of the most commonly used materials in construction industries, mainly in steel structures. There are many researches and studies on the behavior of a structural member of steel structure such as beams under different types of loading. The accurate estimation of rotation capacity (plastic rotation capacity) is of significant importance issue for plastic and seismic analysis and design of steel structures especially for high rise building (nonlinear behavior). Similarly, the moment redistribution in a steel structure also depends on the rotation capacity of the section. So the determination and accurate prediction of rotation capacity of steel structures members such as wide flange beams become an important task. Using different methods such as finite element, regression and statistical methods in previous studies has been used in recent years. Therefore, in order to estimate the more accurate value of the rotational capacity of wide flange beams, Artificial neural networks are used with the Bayesian learning process. The Bayesian regularized network assigns a probabilistic nature to the network weights, allowing the network to automatically and optimally penalize excessively complex models. The proposed technique (BRANN) reduces the potential for overfitting and overtraining, improving the prediction quality and generalization of the network. The proposed model (BRANN) is based on experimental data that collected from previous studies. After a comprehensive review of existing literature, 77 data of wide flange beam were selected which had experienced to determined rotation capacity. For this purpose, Half-length of flange, height of web, thickness of flange, thickness of web, length of beam, yield strength of flange and yield strength of web were consider as input parameters (six inputs) while rotation capacity is treated as target of the Bayesian regularized artificial neural network model. The Bayesian regularized artificial neural network is modeled in MATLAB software and applied to predict the rotation capacity. The results of this model were compared with experimental results and other models and equations that presented in the past (including Genetic programming (GP), Li equation and Kemp Equation. An analysis is carried out to check the performance of the proposed BRANN model based on the common criteria such as Mean Absolute Percentage Error (MAPE). The optimal and best model should have the lowest values of MAPE, this parameter is 20.32% for BRANN, 23.49% for a Genetic Programming model that proposed by Cevik, 47/20% for Li’s Equation and 56.98% for Kemp’s equations. The results of Bayesian regularized artificial neural network approach indicate a good agreement between the predicted and measured data. Furthermore, the Bayesian regularized artificial neural network model shows the most optimized results compared to all the previous model and equations. The result indicated that the Bayesian regularized artificial neural network could be used as a powerful tool for engineers and researcher to solve this kind of problems.
Volume 18, Issue 9 (12-2018)
Abstract
Aerodynamic and optimal design of a blade of a horizontal axis wind turbine (HAWT) has been performed in order to extract maximum power output with considering the strength of the blade structure resulted from different loads and moments. A design procedure is developed based on the Blade Element Momentum (BEM) theory and suitable correction factors are implemented to include three-dimensionality effects on the turbine performance. The design process has been modified to achieve the maximum power by searching an optimal chord distribution along the blade. Based on the aerodynamic design, the blade loads have been extracted and the blade mechanical strength has been investigated by analyzing the thickness of the blade surface and the blade material. The developed numerical model can be considered as a suitable tool for aerodynamically and mechanically design of a turbine blade. The results for a 500 W turbine show that the turbine performance improves by 5% approximately, by modifying chord radial distribution. Yield stress analysis shows the effect of introduced chord distribution on the blade strength, in different blade thicknesses and different blade materials. In addition, optimum tip speed ratio for having favorable mechanical safety factor is derived. Three different airfoil are examined for this investigation and comparing their mechanical safety factor.
Tayebe Shahi, Seid Mahdi Jafari Jafari, Mohsen Pouyan, Mahdi Ebrahimi, Hossein Raghara, Sareh Hosseini,
Volume 18, Issue 121 (March 2022)
Abstract
vinegar is a functional and widely used seasoning around the world that is made from various raw materials. Since there are many reports confirming the antioxidant power of vinegar and its use as a fat burner and weight-loss ingredient, so it is necessary to study the composition and characteristics of different types of vinegars. Jujube vinegar was prepared using different treatments and the best product was selected. Traditional grape and apple vinegars and industrial apple vinegar were also purchased from the local market. physical and chemical tests including acidity, pH, calorimetric, antioxidant capacity, phenolic compounds, sensory and color evaluation were performed on vinegar samples. Based on the results, the minimum and maximum values for pH, acidity, and Brix tests were 2.91 to 3.27, 3.20 to 5.31, and 4.93 to 14.47, respectively. The highest amount of phenolic compounds (5042.67) and antioxidant activity (32.88%) was observed in jujube vinegar. The lowest color components of L, a, and b were 26.11, -5.20, and 32.21 in industrial apple vinegar, respectively. The highest and lowest scores of Average Comparison for taste, color, odor, and general acceptance were observed in jujube vinegar and commercial apple vinegar. The type of raw material and the conditions of the fermentation process have the greatest impact on the quality of the final vinegar the correlation between the color of the traditional vinegar samples and antioxidant properties indicates the presence of more phenolic compounds, which in the case of commercial apple vinegar indicates the presence of caramel in vinegar
Volume 21, Issue 8 (August 2021)
Abstract
New generation of wind turbines, in comparison to the old versions, have been designed with colossal blades to produce larger amount of power output. However, this has led into some unpredictable challenges including their construction procedure and expenses and particularly blades’ transportation. To overcome these issues, multi-rotor wind turbines have been suggested. Aerodynamic performances of such turbines have been previously assessed by other investigators. However, the wake characteristics of these turbines have been less studied. The focus of the present research is on the assessment of these characteristics, which are crucial in the process of any wind farm design. For this purpose, wake flow of a small three-rotor wind turbine is numerically simulated using computational fluid dynamics. A numerical simulation has been conducted for a single-rotor wind turbine and three-rotor small horizontal axis wind turbine with the angle of 180⸰ arrangement. The results of single rotor wind turbine indicated that far downstream wake extended up to 8D, with Jensen-Gaussian model can be better predicted. The comparison between three bladed wind turbine and the results of wake models for the equivalent turbine showed that because of wake interactions in the downstream of the rotor, the loss of turbulent kinetic energy and recovery of the stream speed will be faster. As a result, in the wind farms, the turbines in closer distances around 4D of the equivalent signle-rotor wind turbine can be installed.