Showing 36 results for Shokri
Volume 0, Issue 0 (in press 2024)
Abstract
In order to facilitate the release of floods from the dams and to prevent their damage or collapse, a structure called a spillway is used. Due to the natural and variable flow of the input to the reservoirs of the dams, there are times when the river inflow exceeds the consumption amount in the downstream agricultural lands. In these cases, excess water is discharged over the crest of the weir and flows towards the spillway, which causes high velocities. This high velocity creates low pressure areas on the spillway concrete surface, which can cause major damage to the spillway or even endanger the integrity of the dam structure. Therefore, the dam spillway must safely dissipate the kinetic energy. One of the types of weirs is the stepped spillway to facilitate the passage of the flow over the dams. One of the most obvious practical features of stepped spillways compared to other spillways is the considerable energy dissipation along the spillway. Care should be taken in designing and selecting the type of spillway to prevent potential erosion and reduce kinetic energy as the water flow passes over the spillway. One possible solution is to use a stepped spillway instead of a smooth spillway. In this study, a numeral model of a stepped spillway with different steps and slopes is used. For this purpose, ANSYS software is used for modeling free surface with application of k-ε turbulence model. In the present study, numerical simulation using the Volume of Fluid (VOF) model was used to investigate the mixing phenomenon of two phases of air and water of the free surface flow. The flow field was continued until the residuals reached 10-7. Compared to simpler models such as Mixture, which operates solely on the basis of averaging the properties of two phases, the VOF model, is separating the phases and considering the effects of the interface. The VOF model, is capable of more accurate simulation of phenomena such as fluid mixing, turbulent flows, and heat transfer in multiphase flows. A number of hydraulic specifications which are considered in designing the stepped spillways are the pressure on the surface of the steps, velocity distribution and energy dissipation. The results from the numerical models were compared with experimental studies. They showed acceptable agreement with physical simulations. Results show that discharge and spillway slope increment reduces the amount of energy loss. In the spillway with 5 steps, for a discharge of 0.063 m3/s, the amount of energy dissipation at a slope of 26.6 degrees changes from 85 to 82% at a slope of 45 degrees, which shows a decrease of 3%. With the increase in discharge, the flow depth increases and reduces the effect of the roughness of the steps on the upper layers of the flow. Increasing the height of the steps increases the rate of energy dissipation and also increases the occurrence of negative pressures in stepped spillway. In this case, the contact surface between the main flow and the eddy currents increases. With the increase in the height of the steps, the dimensions of the rotating vortices also increase and cause a larger radius of rotation on the steps. The presence of these large rotating vortices separates the flow from the bottom of the steps and reduces the pressure on the surfaces. The number and dimensions of steps can alter the energy dissipation rate. Increase in the number of steps in a spillway with constant height, reduces the energy loss as the result of steps dimensions being shrunk
Volume 2, Issue 1 (7-2021)
Abstract
Introduction:
Cities, as the main areas of human life, consist of components and elements such as open and public spaces. Today, advances in digital technology in various fields, including public spaces, have had a tremendous impact.
Aim:
The purpose of this study is to address the impact and effects that cyberspace has on public spaces and their presence.
Materials and Method:
Based on its objectives, the research is fundamental and is in the category of descriptive and explanatory-analytical studies. After reviewing the basics related to smart city and public spaces by referring to valid documents and texts, the impact of cyberspace on urban public spaces has been considered and according to the criteria of presence in space, 100 questionnaires of Tehran citizens have been completed and analyzed.
Findings:
Findings show that most people use cyberspace as a stimulus and tool to be in public and not as a competitor to not be in public. However, this trajectory in Iran is close to the average because some people (older or with special characteristics) still use cyberspace and the mentioned technologies in a more limited way.
Results:
The results show that cyberspace serves citizens as a stimulus to increase their presence in public spaces. Therefore, it is necessary for urban planners to try to improve services and use cyberspace and technology as a tool to facilitate the presence in cyberspace.
Volume 2, Issue 3 (9-2014)
Abstract
Since the change of land use accrued in the Iran, especially in northern Iran, this research aims tocompare the spatial variability of soil properties in three adjacent land uses including cultivated by wheat lands, grazing lands and forest Lands covered by juniperus sp, fagus orientalis, quercus castanifolia, and acer velotinum species in kiasar region, Mazandaran Province, northern Iran. Some of soil features, i.e. pH, CaCO3, total nitrogen (TN), soil organic carbon (SOC), electric conductivity (EC), percentage of silt, clay and sand contents and saturation moisture content(SM) were measured at a grid with 20 m sampling distance on the top soil (0 – 30 cm depth). Accordingly, total of 147samples were taken from 49 soil sites. The normality of data was examined by the tests of normality. Then, data were analyzed by using of geostatistics approach. The results showed that spatial distribution of many soil properties could be well described by spherical model in the forest and exponential model in the cultivated and grazing lands. Spatial dependences were the highest for SOC, EC and the lowest for silt, (SOC and silt) in the forest method and grazing lands, respectively. Deforestation and conversion to cultivated and grazing lands decreased spatial dependence of soil properties.
Volume 6, Issue 2 (9-2014)
Abstract
This paper examines the characteristics and vulnerabilities of the second Pahlavi and its role in the revolutionary mobilization. The main question of the paper is that: what are the characteristics and vulnerabilities of the Shah's government that led to the revolutionary mobilization? To answer this question, document analysis has been used that is a kind of qualitative research. By this method, documents including books, articles and dissertations have been investigated. Therefore, in this paper, the combination of state–centric theories including the theories of independence of state, capabilities of state, political opportunities of state, and construction of state were used to develop a model to explain the status of the Pahlavi state and also its vulnerabilities, and also its relation to revolutionary mobilization. The findings showed that the most important vulnerabilities of Pahlavi state include independence of the Pahlavi rentire state from the social classes, discapabilities of the state in policy making, bureaucratic weakness of the state institutions, state monopolies, and vulnerabilities resulting from modernization, and roforms, which in combination with each other led to the revolutionary mobilization.
Volume 8, Issue 1 (4-2008)
Abstract
Health Systems aim to improve health by delivering health care services. But sometimes in low-income countries, people become poor when they use these services. So, it is required to analyze the experience of health system financing in the selected countries and develop strategies to improve the efficiency of health system financing.
The objective of the paper is to identify the main determinants of health care expenditures in 10 OECD countries over the period 1998-2004. The major determinants of health care expenditures which are theoretically identified comprise the total government revenue earned from health care system, social security expenditures on health, Out-of-pocket expenses on health, and the ratio of ex ante payments of private sector on health over the total health expenditures.
The stylized facts of the study shows the principles of equity-base health policy planning are notification of financing mechanisms in health sector, identity of financing model according to the county socioeconomic conditions, financial capacity, infrastructure, capability of implementing selected policies, political responsibility and accountability for these policies.
Volume 10, Issue 1 (Winter 2019)
Abstract
Aims: Thymus Garden (Thymus vulgaris L.) is one of the economically important plants which is extremely sensitive to oxidative stress and drought stress during germination time. Salicylic acid, as an herbal hormone, plays an important role in increasing plant tolerance to biotic and abiotic stresses. The current study was conducted aiming to increase the plant resistance to environmental stress by increasing its enzymatic and non-enzymatic antioxidant capacity by salicylic acid treatment.
Materials & Methods: In this experimental study, the plant seeds were soaked in 2mM salicylic acid solution a randomized complete block design with three replicates for 16 hours, and they were then planted in pots. Pots were transferred to growth chamber with constant and controlled conditions for 16 hours of light: 8 hours of dark at a temperature of 25°C for 14 days. At the end of the experiment, the growth parameters of plants, germination percentage, phenol content, and the activity of the important antioxidant enzymes, such as superoxide dismutase, catalase, polyphenol oxidase and peroxidase, were measured and compared with the control group.
Findings: Although salicylic acid did not have a significant impact on plant growth, it has led to an effective of antioxidant enzymes in the plant. Moreover, this treatment has increased the antioxidant content of the plant.
Conclusion: Treatment with salicylic acid could result in an increase in Garden Thyme tolerance to stress conditions.
Volume 10, Issue 2 (Vol. 10, No. 2 (Tome 50), (Articles in Persian) 2019)
Abstract
Among the various types of rhetorical figures applied in Shahnameh, metaphor is one of the most effective examples of rhetorical devices. Ferdowsi has been able to imagine, exaggerate, move and depict it at the same time by using it as a means to create discursive space and dialogic atmosphere.
Since we encounter with the text of discourse in the Shahnameh, we find that every word is a way toward the perception of the former and a way to perceive the word of the future. Each word treats another word or it targets the belief system of the target audience.So, braggadocio is a dialogic- discursive system in which metaphore plays a key role. According to Bakhtin's theory, there is a close relationship between dialogue and polyphony, and language is also "dialogic" in its nature, regardless of what the answer will actually be.
Polyphony is also a dialogic feature, and Shahnameh is also a Polyphonic- dialogic text. The purpose of the present research is to investigate the relationship between the braggadocio of Shahnameh with making narration by relying on Bakhtin's dialogic theory and its relationship with metaphor, and to show how this feature interferes with the restoration of action, suspension, and delay. It can lead to a dialogic atmosphere and extend it to transfer actions.
Mahmood Shokrieh, Sayyed Mostafa Mahdavi,
Volume 11, Issue 3 (9-2011)
Abstract
Carbon Nanotube (CNT) dimensions and interphase region are the important parameters that affect on the mechanical behavior of CNT/Polymer composites. In this study, a new analytical model is established to predict the modulus of these structures. Considering the influence of CNT dimensions (diameter and length) an interphase region, the elastic modulus of nanocomposite is determined. In this new model, a nanotube with hollow cylindrical structure is modeled as a transversely isotropic solid nano-fiber. Moreover, interphase region and its van-der Waals interaction is simulated as an isotropic hollow cylindrical solid that its mechanical properties is derived using the continuum mechanics. To predict the modulus of nano-composites, a representative volume element (RVE) containing a transversely isotropic solid nano-fiber, isotropic solid interphase region and the matrix is employed using Halpin-Tsai model. Finally, the results of the proposed analytical model are compared with various available experimental results. The proposed model is simple and the results obtained by the model are in good agreement with available experimental results.
Volume 12, Issue 4 (12-2023)
Abstract
Investigating the trend of temperature changes occurring in the Persian Gulf can be used to determine the pattern of climate change in the region and to study the impact of these changes on aquatic habitats in the Persian Gulf waters. This study was carried out to investigate the changes in sea surface temperature and sea surface temperature anomaly in Kharg and Hendourabi islands by using Environmental Research Division's Data Access Program (ERDDAP) of National Oceanic and Atmospheric Administration (NOAA) and daily sea surface temperature and sea surface temperature anomaly were investigated over a 35-year period.The results showed that the average annual surface temperature increased by about 1 °C over 35 years in Kharg and Hendourabi Islands and the average annual sea surface temperature anomaly in these islands were increased by 2 °C. The slope of this increasing trend on Kharg Island was more severe than Hendourabi Island. The most significant bleaching event in the Persian Gulf occurred in 2016-2017, with the highest increase in temperature in 2017. As water temperatures continue to increase in the coming years, the living conditions of the Persian Gulf corals are likely to deteriorate, and only some resistant species can survive in the Gulf.
Ebrahim Hajidavalloo, Vahid Shokri, Morteza Behbahani-Nejad, Younes Shekari,
Volume 13, Issue 1 (4-2013)
Abstract
Abstract-Two-fluid models are the most accurate and complex models for analysis of two-phase flows. There are two different two-fluid models for analyzing compressible isothermal two-phase flows which are Single Pressure Model (SPM) and Two-Pressure Model (TPM). In spite of capabilities of these models in capturing two-phase flow behavior, it is not possible to express them in conservative form due to existence of non-conservative term in momentum equation of phases. Therefore, the classical Rankine-Hugoniot condition across discontinuities in the flow filed is not applicable for these equations and there would be difficulty in using classical numerical methods for solving these equations. In this paper a new path-conservative method is used to overcome this difficulty. In this method, one can apply general Rankine-Hugoniot condition along a path connecting left and right states of the discontinuity. After expressing path-conservative form of the employed central numerical methods which are Lax-Fridriches, Lax-Wendroff and Rusanove, water faucet and large relative velocity shock tube problems are solved by using these schemes. Grid independence was achieved using different grid sizes. For water faucet problem, comparison of numerical results with analytical solution show good agreement and for shock tube problem, the results indicate that this method is highly capable in capturing discontinuities in two-phase flow.
Mahmod Mehrdad Shokrieh, Afshin Zeinedini,
Volume 13, Issue 13 (First Special Issue 2014)
Abstract
In this paper, the equivalent layup method to estimate the delamination initiation of asymmetric double cantilever beam (ADCB) is presented. A relation for critical strain energy release rates (SERR) of unidirectional (UD) and multidirectional (MD) laminates, as a criterion for crack growth initiation, was presented. For finite element analyses, the ADCB specimens were modeled in ABAQUS/Standard software and SERR is determined using the virtual crack closure technique (VCCT). According to this method, the ability of estimating delamination initiation without using experimental tests and finite element modeling of MD specimens is provided. This method reduces the volume of calculations FEM and experimental tests significantly. Accuracy of the proposed method has been verified by experimental data. Also, the total strain energy release rate analyzed by this method is compared with the FEM and theoretical results. Results show that SERR of MD lay-ups can be predicted by measuring SERR of the unidirectional specimens using FEM method with an error less than 10%.
Volume 13, Issue 59 (0-0)
Abstract
Celiac is life-long intolerance to the glidin fraction of wheat and the prolamins of rye (secalins), barley (hordeins) and possibly oats (avidins). The most challenging products to formulate and produce are gluten- free bread and pasta, as gluten is their structure-building protein. The purpose of this research was to evaluate effect of Hydroxy Propyl Methyl Cellulose (HPMC) gum and Microbial Transglutaminase (MTGase) enzyme on farinograph properties of dough and quality characteristics of pasta. For this purpose HPMC at three levels (1%, 1.5%, 2%) and MTGase at three levels (0.3 %, 0.5%, 0.7 %) were added to formulation. Results showed that addition of HPMC and MTGase increased dough development time, decreased degree of dough softening, cooking loss and stickiness of pasta. In addition HPMC increased dough stability time, water absorbtion and moisture of pasta. While MTGase had no significant effect on this parameters. Also the colour test analysis results showed that addition of HPMC and MTGase had no significant effect on the colour of pasta. Finally results of sensory evaluation showed that pasta containing 2% HPMC and 0.7% MTGase had high mean score for texture and overall acceptability compared to control.
Hamed Ahmadi, , Mahmoud Mehrdad Shokrieh,
Volume 14, Issue 2 (5-2014)
Abstract
Syntactic foams are a kind of composite; consist of polymeric matrix and hollow micro-balloons. They have high strength to weight ratio if it compare to the neat matrix material. In this paper epoxy resin as matrix and ceramic micro-balloons are used and 36 kinds of syntactic foam were fabricated to investigate the effect of preparation factors such as: mixing speed, mixing time, mixing sequence and extracting bubbles by a vacuum oven on the mechanical properties. Also, two undesirable events like micro-balloon flotation in matrix and porosity are investigated as they affect the foam`s strength. The results show that the speed and sequence of mixing are not effective seriously. However the time needed for mixing would be changed for different volume percent of micro-balloons. It should be noted that as flotation and porosity increases the compression strength decreases. Using the vacuum pressure before molding may decrease the matrix porosity for above 40% micro-balloon volume fraction syntactic foams. Converse to previous, using the vacuum pressure for below 40% micro-balloon volume fraction syntactic foams would increase the floatation and decreases the compression strength.
Volume 14, Issue 2 (Summer 2010)
Abstract
In most of the legal systems, to guaranty the loans, there are two types of collaterals: Fixed charge ands Floating charge. The first type often occurs in tangible properties and assets while the second one has an ability to occur in the debtor's whole assets. Floating charge, which has been recognized in Article 9 of the Uniform Commercial Code, has been considered to create security interest in the debtor's future assets and also to create trust about the maintenance of mortgage on alienable properties. Precision, coherence and comprehensiveness of this Article have been inspired by most of the legal systems in codification of the rules of mortgage contracts. Although there are some regulations about mortgage contract in the Civil Code of Iran, taking securities from asset's value and future's benefit has been permitted to facilitate loan receiving in manufacturing plans since 2007. In this research, such a new regulation is studied comparatively in both contexts of Iranian and American legal systems.
Volume 14, Issue 3 (Fall 2024)
Abstract
Aims: During the 1960s to 1980s, urban planning changed from a completely elitist and value-free perspective to a value-based and participatory model. interactive planning as one of the most important contemporary heritages of urban planning has received the attention of professionals in this field. The research aims to identify interactive planning factors as perceived by professionals in the contemporary period.
Methods: The research method has been done in terms of applied type and with a combined (quantitative-qualitative) method. After extracting the indicators by reviewing the sources, 175 questionnaires were completed by Urban planning professionals. Cronbach's alpha of the data was calculated and then the factor analysis method was implemented.
Findings: Cronbach's alpha of the data was 0.930, which indicates the high reliability of the research data for further analysis. The research findings after 10 varimax rotations showed 6 factors with a variance close to 60% (58.63) for extraction.
Conclusion: The results of the research indicate that from the point of view of contemporary urban planning professionals. factors such as contributing citizens, giving them the power of citizenship, transparency, and awareness, supporting institutions, pluralism, a sense of belonging, and The responsibility of citizens have an impact on this type of planning. Therefore, it is suggested that managers, planners, designers, and all factors affecting urban planning pay attention to the mentioned factors in order to promote interaction So that interactive planning (one of the contemporary heritages of urban planning) provides the context for participation and interaction and as a result more effectiveness.
Hamed Ahmadi, , Mahmoud Mehrdad Shokrieh,
Volume 14, Issue 4 (7-2014)
Abstract
Epoxy / ceramic micro balloon syntactic foams are used in marine and automobile industries because of their high specific strength and capability of absorbing energy. In this paper, the neat epoxy and 9 series of syntactic foams with 3 kinds of ceramic micro balloon with different diameters and crush strength in different volume fractions (20%, 40% & 60%) were fabricated. Effect of varying these parameters on the mechanical properties of syntactic foams is investigated. Besides of all, the effect of different loading rate is investigated, too. All of the samples were tested in 10-1, 10-2 and 10-3 strain rates. The results indicate that with increasing the strain rate from quasi-static to moderate rates, the strength of foams became more. Also the results show that the syntactic foam with bigger micro balloon was weak in compression. In syntactic foams of low volume fraction the size effects is more. On the other hand, with increasing the volume fraction, the crush strength of micro balloon is become effective. Plateau stress and absorbed energy results show these facts obviously. With increasing the strain rate, the strength is increased considerably.
Mahmood Mehrdad Shokrieh, Reza Mosalmani, Salem Soveity,
Volume 14, Issue 9 (12-2014)
Abstract
One of the most applicable methods to study the mechanical behavior of reinforced polymers with CNTs is modeling of representative volume element (RVE). It has been shown that the mechanical behavior of RVE depends on its ingredients mechanical properties and its geometrical parameters. In this research, a RVE which includes a CNT and its surrounding polymer is chosen as a rectangular cube. In this research, effects of the length and depth of the RVE, the length of the CNT and the CNT caps on the elastic behavior of the RVE have been studied. Furthermore, the effect of the volume fraction of CNTs is also considered. First, an analytical solution has been developed to predict the elastic modulus of the RVE. Then, using a finite element method, the elastic behavior of the RVE is modeled. The analytical and numerical results show that at a constant volume fraction of the CNT, variation of each material and geometrical parameters can affect the longitudinal elastic modulus of the RVE significantly. However, it has been shown that the transverse elastic modulus of RVE is not sensitive to the geometrical parameters variations. Finally, using a combination of the Halpin-Tsai micromechanical model and the present analytical solution, a proper aspect ratio of the RVE for each volume fraction of the CNT has been determined and suggested.
Mahmood Mehrdad Shokrieh, Reza Madoliat, Bahador Bostani, Ahmad Ghasemi, Vahid Mohmoodian,
Volume 15, Issue 1 (3-2015)
Abstract
In the present paper, a new combined technique consist of experimental results and numerical solution for determination of elastic constants of thin and thick orthotropic plates with various stacking sequences; and also isotropic plates under different boundary conditions is proposed. This new proposed technique makes use of vibrational test data, corresponding numerical solution and optimization methods. The vibration test data consists of a set of eigen frequencies that are obtained from transverse vibration test of the plate. The numerical solution is based on a finite element method using a commercial program. Material constants of the plate are determined by using of the inverse method and a particle swarm optimization algorithm in MATLAB software. The error function is based on the sum of square difference between experimental data and numerical data of eigen frequencies solution. The validation, performance and ability of the proposed technique in this paper are discussed using experimental and numerical data available in the literature. The higher accuracy of results that obtained by the present method in comparison with other methods proved the validity and capability f the new proposed method.
Mahmood Mehrdad Shokrieh, Ali Reza Shamaei Kashani, Reza Mosalmani,
Volume 15, Issue 7 (9-2015)
Abstract
Mechanical properties of polymeric materials are significantly sensitive to the loading rate. Therefore, it is necessary to develop a dynamic constitutive model to investigate their strain rate dependent mechanical behavior. In this study, first by conducting torsion experiments the shear behavior of neat and reinforced epoxy with carbon nano-fibers (CNFs) was studied experimentally. Then, the Johnson-Cook (J-C) model has been modified to be able to model the shear behavior of neat polymers. The strain rate effects on elastic behavior of polymers were considered by introducing a material equation. Then, by combining the modified Johnson-Cook (MJ-C) model with a micromechanical model (Halpin-Tsai model) and using pure polymer experimental tesults and mechanical properties of carbon nano fiber, the strain rate dependent mechanical behavior of polymers reinforced with CNFs at arbitrary strain rates and volume farction of carbon nanofiber has been predicted. The new model presented in this research is called as the dynamic-micromechanical constitutive model. The predicted results for the neat and nano-phased polymers were compared with conducted and available experimental results. It has been shown that the present dynamic constitutive model can predict the strain rate dependent mechanical behavior of polymeric materials with a good accuracy.
Mahmood Mehrdad Shokrieh, Afshin Zeinedini, Seyed Moahmmad Ghoreishi,
Volume 15, Issue 9 (11-2015)
Abstract
The purpose of the present research is to investigate effects of long multiwall carbon nanotubes (MWCNTs) on mechanical properties of epoxy resin and unidirectional glass fiber reinforced laminated polymeric composites. Therefore, mechanical properties of polymer (pristine resin), 0.5 wt.% MWCNT/epoxy nano-composites, E-glass/epoxy laminated composites and 0.5 wt.% MWCNT/E-glass/epoxy laminated nano-composites were evaluated. The tensile, flexural and shear moduli and strengths of epoxy polymer and nano-composites were experimentally characterized. Next, the longitudinal and transverse tensile stiffness and strength, also in-plane shear and flexural moduli and the strength of glass fiber laminated composites and glass fiber laminated nano-composites were determined. The experiment results of tensile specimens of laminated nano-composites reveal that the presence of the long MWCNTs improves the bounding properties of fibers in adjacent plies and postpones the failure mechanisms like fiber fracture under tension or edge delamination under shear loading conditions. It can be concluded that the improvement of mechanical properties in laminated composites are more significant than those of the pure epoxy with addition of long multiwall carbon nanotubes. For instance, the longitudinal tensile strength and shear strength of laminated nanocomposites increased by 34% and 26% in comparison with laminated composites, respectively.
