Showing 7 results for Mohammadipour
Volume 3, Issue 5 (Supplementary Issue - 2014)
Abstract
The Leopard moth, Zeuzera pyrina (L.) (Lepidoptera: Cossidae) is a serious pest of walnut and apple trees in Iran. One of the control methods for this pest is the mass trapping of males using pheromone traps. To determine the best size and color of traps, four different colors (green, yellow, white, gray) and two different sizes (delta shape with standard adhesive surface, 19 × 22 cm and trapezoidal shape with twofold adhesive surface, 36 × 22cm) were compared in a walnut orchard in Alborz province. The results showed that color did not have any significant effect on the number of males captured by traps, whereas the newly made, trapezoidal trap could capture more than twice as many as a delta trap. This means that with the same number of pheromone dispensers, more than twice as many moths could be captured by trapezoidal traps than by delta traps, which could increase the efficiency of pheromone traps in an Integrated Pest Management (IPM) program.
Yaser Basati, Omid Reza Mohammadipour, Hamid Niazmand,
Volume 17, Issue 6 (8-2017)
Abstract
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.
Mohamad Hossein Mohammadipour, Mohammad Golzar,
Volume 17, Issue 6 (8-2017)
Abstract
This paper presents a numerical model for predicting pressure, impregnation and pulling force in pultrusion die which circular cross section witch two reinforcement fibrous tows pass through it. Pulling force and degree of impregnation are the most important parameters associated with pultrusion process that determine production cost and quality of pultruded profile respectively. Main idea in this approach is obtaining characteristic equations in purely polymer region and purely fibrous region and establishing relations between them by using conservation law. The superiority of this approach compared to other methods is ability to considering both straight and conical part of the die, calculating pulling force, ability of investigating influence of a variety of parameters such as those associated with die geometry, material rheology and process parameters. In this paper the influence of fibers position and fibers radius on pulling force, impregnation and pressure inside die is investigated. Due to the ability of simultaneous calculation of force and impregnation, this model can be used to establish an optimum condition between cost and quality of produced profiles.
Dariush Mohammadipour, Amir Farhad Najafi, Hamed Alemi Arani, Alireza Riasi,
Volume 17, Issue 9 (11-2017)
Abstract
Recently, use of PAT (pump as turbine) in mini hydro power plants (< 500 Kw) has increased due to its lower cost, easy installation and maintenance feasibility. Since the overall efficiency of this machine is lower than conventional turbines, the use of these machines in large plants are not economically recommended. In this study, the effect of geometrical parameters of impeller on PAT performance is investigated. In the present research, the geometries of components of an available commercial pump was scanned and modeled. To make the study more feasible, Impeller was redesigned in CFturbo software. Commercial software of ANSYS CFX 15.0 was used to simulate the fluid flow within PAT. Numerical results are in good agreement with existing experimental data. Three main parameters, namely, blade number variations, leading edge shapes and splitter blades were comprehensively investigated. Result shows that using 7 blades, rounding leading edge with suction side chamfer and 20% length splitter blades improve the efficiency. Finally, the most appropriate geometry with parameters of 6 blades, rounded trailing edge with suction side chamfer and 20%splitter blades is recommended for achieving the highest efficiency that can boost it up to 2%.
Yaser Basati, Omid Reza Mohammadipour, Hamid Niazmand,
Volume 18, Issue 1 (3-2018)
Abstract
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.
V. Dabirpour, O.r. Mohammadipour,
Volume 19, Issue 3 (March 2019)
Abstract
In this study, convective heat transfer around a heated circular cylinder covered with an annular porous medium in a flat channel was numerically investigated. To enhance the heat transfer, the porous medium is chosen to have a high thermal conductivity, whereas it is equipped with two different dispersions to reduce the pressure drop through the channel. To create two different dispersions (bi-disperse porous medium), the cylinder is covered uniformly by multiple porous fins with a porosity of 0.9. In this regard, the fin porosity will be the first levels of porosity (microscopic porosity) and the arrangement of fins will be referred to as the second levels (macroscopic porosity) of the porous medium. The main goal of this research is to investigate and optimize flow conditions to achieve the highest outlet temperature and the highest heat transfer rate, where the pressure drop is reduced to a minimum value. This optimization is carried out for flow Reynolds number of 60 to 120, the Darcy number of 10-3 to 10-5, macroscopic porosity of 0.25 to 0.75, and outer to inner fin ratios of 1.5 to 2. Numerical simulations are conducted, using the lattice Boltzmann method and the validity of simulations is assessed by the use of numerical and experimental data available in the literature. To optimize, the response surface methodology (RSM) with a central composite design is used and numerical results indicate that predictions obtained by RSM are in good agreement with actual flow condition in the optimum configuration. This research can provide new insight into the optimization process in heat exchanger designs.
Volume 22, Issue 4 (winter 1401 2022)
Abstract
Introduction
Considering the international policy towards sustainable development and conflict of the energy subsidy with the SDG, the present study examines the effects of subsidy on the realization of sustainable development in the selected countries. For this purpose, by designing and constructing a Composite Indicator (CI) for sustainable development, the performance of the top five countries in the world in terms of paying the most energy subsidies (first group), is compared with the performance of the world's large economies in terms of the highest rate of GDP (second group, mainly without paying energy subsidies). The hypotheses of the research are: 1) there is a negative relationship between the rankings of countries in terms of the largest energy subsidies with the ranking based on the realization of sustainable development. 2) the countries of the second group (with the lowest energy subsidies) have on average a better situation in achieving sustainable development compared to the countries of the first group. 3) among the countries of the second group, China has the least realization in sustainable development by paying significant energy subsidies.
Methodology
In the present study, the composite index of sustainable development is investigated using 12 variables in the form of three economic, social and environmental dimensions and based on the design of Multiple Attribute Decision Making (MADM). The targeted CI is calculated using seven approaches: Z-Score, Max-Min, McGranahan, Experts’ Judgements Scoring, Guttman, TOPSIS and VIKOR, for selected countries over the period of 1990-2020, and the results are presented and compared at static and dynamic levels. To weight the variables, the same weighting technique, McGranahan, EJ scoring, Guttman and CRITIC (Criteria Importance Through Intercriteria Correlation) are used in the calculations.
Findings
The results of the study indicate the unfavorable situation of Iran in paying energy subsidies (ranked first in the world) and the realization of sustainable development (ranked last among the countries surveyed); Germany, on the other hand, ranks first in the study without paying energy subsidies. Ranking countries at the dynamic level, while eliminating the existing problems at the static level, indicates a strong negative relationship between paying energy subsidies and achieving sustainable development. This confirms the first hypothesis of the research. In this regard, the correlation between the average energy subsidy and SDIMax-Min has been increased to -0.74 and the ranked correlation between SDIMax-Min and subsidy payment has been improved to -0.85. On the other hand, the average values of sustainable development indicators, with the change of study approach and weighting techniques, have had similar and stable results, which all indicate that the ranking of countries in different situations has become more realistic in the dynamic level compared to the static level. Also, the comparison of the average sustainable development realization in the first and second groups, shows that in terms of quantity and rank, the countries of the second group have a significant advantage over the first group, which means confirming the second hypothesis. And finally, in the ranking based on 7 approaches, China is ranked 4th after Germany, America and Japan in 6 approaches, which means confirming the third hypothesis. The results of sensitivity analysis indicate the high share of life expectancy, per capita income and education index in the targeted CI.
Discussion and Conclusion
Regarding some minor differences in the results of the seven approaches, using De Montis et al. (2021)'s experience based on calculating the average ranks and Miç & Figen Antmen (2021)'s experience based on setting the criterion of the highest repetition of the rank in different approaches, all hypotheses are confirmed and the ranking of the countries does not change. Also, if we perform a sensitivity analysis on the approaches, there will be no change in the final ranking result. The main suggestion derived from the results of the research is the necessity of planning to eliminate energy subsidies in the country in accordance with international policies from 2015. However, according to Mohammadipour et al. (2022), the removal of energy subsidies and the modification of the energy carriers’ prices creates very extensive and lasting (long-term) destructive effects on macroeconomic variables. On the other hand, according to Taylor (2020), based on the REmap (Renewable Energy roadmap analysis) by IRENA (International Renewable Energy Agency), firstly, policy development in the direction of renewable energy, nuclear, etc., and planning to reduce fossil fuel subsidies have been identified in the form of two axes (until 2030 and until 2050). And secondly, a special path has been drawn to manage and move from harmful subsidies to the environment and sustainable development to environmentally friendly subsidies until 2050. Therefore, considering the destructive effects of energy subsidies, it is suggested that all reforms and removal of energy subsidies should be carried out in the form of a comprehensive, regulated, gradual program with a strong redistributive role of the government. Secondly, all these actions should be done in line with the global planning and policy and taking into account the REmap. Also, the research results of the study suggest that in the design of MADM models, when the data are of the time series type, Z-Score, Max-Min, McGranahan, Experts’ Judgements Scoring and Guttman approaches perform better (and more recommended) by replacing the opposite variable for each time series data. However, when the data are not in the time series form, the performance of TOPSIS and VIKOR approaches are optimal (and more recommended) by simplifying complex relationships.
