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Showing 230 results for Dehghan
Volume 23, Issue 6 (11-2023)
Abstract
Abstract
Due to the mechanical behavior of brb braces and concrete frames differing, combining these shows complex behavior in a seismic. It can be used to dual system Brb-Rcf in a concrete moment frame to Improve structural responses. Considering that the behavior of the BRB brace in compression and tension is similar; It can solve the unbalanced force in the Double-K bracing system. The desirability of the Double-K arrangement and its combination with the RCF system as a dual system should be investigated in order to investigate the possibility of using Double-K braces in the RCF system and reducing residual deformations in the case of the dual system. For this purpose, a series of buildings have been analyzed and designed in three structural systems: Rcf, dual frame with brb brace, and bare frame with brb brace according to relevant valid regulations. The pushover and time history analysis have been done, and the capacity curves, base shear, and residual deformation have been investigated and studied. Adding brb braces to the concrete moment frame and dually using them increased the structure's capacity. In the studied structures, from 84% increase capacity in 4-story structure to 94% increase capacity in 12-story structure. This increase is due to the interaction of the concrete moment frame and the brb braces in a dual system. Also, the use of brb braces has made the structure repairable. Because in the concrete structure of the moment frame and the bare frame, the failures were concentrated in the beams and a little in the columns, respectively, but in the structure with Brb-Rcf, the losses were mainly transferred to the braces, which are easily replaceable. Also, the reduction of residual deformation of the structure reduces causes the cost of repair and reconstruction in the structure. Investigations on the formation of hinge showed Due to the Double-K brace that no hinge was formed in the middle of the columns. the losses were mainly transferred to the braces, which are easily replaceable. Also, the reduction of residual deformation of the structure reduces causes the cost of repair and reconstruction in the structure. It was also observed that the structure in combination with the brace in the Brb-Rcf system is designed more economically and with fewer consumables. It is shown in the structure of 8, 4 & 12 story; that the base shear has increased in the frames with brb braces and this increase has been greater in the dual system due to the bending frame and the brb braces. Also, in the hinge, it was observed that the failures of the double structure were less and the types of failures were better according to the replaceability. In general, due to less failure and more base shear that the dual system structure has, it can be said that the stiffness and resistance due to the interaction of the bending frame and the non-buckling brace has increased, which is the result of the good performance of the dual structure. By comparing the base shear, the suitability of these values with the bearing analysis is clear, so that there also the results showed the increase of the base shear due to the interaction of the frame and the non-buckling brace.
Volume 23, Issue 10 (October 2023)
Abstract
Currently, dissimilar metal joining processes are receiving considerable attention in various industries. The objective is to create composite structures that are both high-strength and lightweight, ultimately reducing the weight of the final product. Researchers have recently proposed friction drilling as a new method for creating joints between dissimilar metal sheets. This innovative technique offers potential advantages in achieving the desired outcomes. In this process, metal sheets are placed on top of each other and simultaneously subjected to friction drilling. As a result, this process not only creates an effective space for tapping but also establishes a frictional joint between the two sheets. Research has shown that preheating up to 350°C can have desirable effects on reducing the gap between the two sheets in the vicinity of the created joint between aluminum and stainless steel using the above-mentioned method. In the upcoming work, the effect of preheating on tool wear in simultaneous friction drilling of aluminum sheet AA6061T6 and stainless steel AISI304L using a tungsten carbide drilling tool has been experimentally analyzed, and the findings indicate that increasing the preheating temperature up to 350°C leads to a 13.77% increase in tool adhesive wear and a 0.46% increase in tool abrasive wear.
Volume 23, Issue 10 (October 2023)
Abstract
In this research, the effect of parameters of cutting speed, feed rate and machining time at constant cutting depth on tool wear and its effect on the surface roughness of hardened steel 4140 and machining forces were investigated. First, 4140 steel was prepared and its hardness was increased to 45 HRC under heat treatment, and then the TCMW 16T304 H13A tool was prepared from uncoated cemented carbide for machining. The design of the experiments was carried out in a full factorial manner. The analysis of the results was done from the analysis of variance test and the graphs related to the experimental results, based on these results, the advance rate had the greatest effect on the surface roughness and machining shear force, and the machining time had the greatest effect on the machining advance force and Cutting speed also had the greatest effect on tool wear. The highest amount of tool wear was equal to 0.89 mm and the lowest amount of tool wear was equal to 0.41 mm. The best surface quality was measured as 0.372 μm and the highest surface roughness was measured as 1.154 μm. The maximum shear force was 172.7 N and the minimum shear force was 54.2 N. The maximum forward force was equal to 156.59 N and the minimum forward force was equal to 45.86 N.
Volume 23, Issue 10 (October 2023)
Abstract
The ability to predict tool wear during machining is a very important part of diagnosis, which makes it possible to replace the tool at the appropriate time. Therefore, in this research, the artificial neural network approach was used to predict tool wear. First, hardened steel 4140 was turned with uncoated cemented carbide tool TCMW 16T304 H13A and with input parameters including cutting speed, feed rate and machining time in three different levels and with constant cutting depth, and the amount of tool wear was measured. And the experimental test results were used to train and validate the artificial neural network. The optimal neural network architecture was obtained with 3 nodes in the input layer, two hidden layers with 12 and 36 nodes in the first and second hidden layers, and 1 node in the output layer to predict tool wear. The prediction values of the artificial neural network model were compared with the experimental results and the average error percentage of the validation data was calculated as 3.32%.
Volume 23, Issue 10 (October 2023)
Abstract
When working with hardened materials, it's important to control and optimize the surface roughness and machining force. To achieve this, we can use intelligent methods that are based on prediction and optimization models. In this study, an artificial neural network was used to evaluate the surface roughness and machining force of hardened steel 4140 by analyzing cutting speed, feed rate, and machining time. A full factorial method was used to carry out 27 experiments, and an uncoated cemented carbide tool TCMW 16T304 H13A was used to measure surface roughness and machining force during turning. An artificial neural network model with two hidden layers was selected as the optimal architecture for separately predicting surface roughness and machining force. The predicted values were then compared with the experimental results, and the average error percentage for validation data was calculated as 4.25% for surface roughness and 5.11% for machining force. Finally, the optimal cutting parameters were selected to minimize surface roughness and machining force.
Volume 23, Issue 12 (December 2023)
Abstract
To investigate the effect of relative humidity percentage on heat transfer and distribution of droplets in the condensation phenomenon, a test device with the ability to provide and control different environmental conditions was made, and therefore, the hydrophilic (copper) and hydrophobic (Teflon coating on copper) surfaces were measured under controlled environmental conditions. In all the tests, the inlet air flow rate, inlet air temperature, air temperature reaching the test surface, water temperature, water surface height, and test surface temperature were kept constant at specific values using PID control. Each test's relative humidity values of 80, 88, and 96% have been determined and controlled. The results of the transient investigation of heat transfer show that it takes time for the condensation phenomenon to occur, and the higher the surface hydrophilicity and relative humidity, the shorter this time will be. Also, the average heat transfer for 60 minutes was calculated. It showed that the average heat transfer coefficient increases with increasing humidity. Under the same environmental conditions, the heat transfer coefficient on hydrophilic surfaces is higher than on hydrophobic ones. In the graphical analysis of the droplet size, it has been observed that the most oversized droplets on hydrophilic surfaces at relative humidities of 88 and 96% are in the hydraulic diameter range of 0.35 to 0.4, and on hydrophobic surfaces are at relative humidities of 80 and 88% in the hydraulic diameter range of 0.2 to 0.25 mm.
Volume 24, Issue 2 (6-2020)
Abstract
One of the new approaches to development is the good governance model, which can be achieved through e-governance. Given the extensive literature and the lack of a comprehensive and indigenous model for good e-government in the country, the present study aims to design a model for the establishment and development of good e-governance based on systematic review of articles and their analysis using a Meta-synthesis method. For this purpose, after searching the databases in the period of 2000 to 2018, finally 85 articles were selected and by analyzing their content, the relevant dimensions and codes were extracted and the importance and priority of each was determined using Shannon entropy. Based on research findings, Information and communication technology codes, Human resources with knowledge and skills in the use of information and communication technology, Confidentiality of information, network security, credibility and reliability of information, the reality of security laws, the validity of the information provided, the entry of legal procedures and civil society oversight of e-government performance, ease and convenience of citizens in using services and access to government information and the reduction of government spending were the most important factors among the 19 dimensions of establishing and developing good e-governance. Finally, After the research steps, the model of establishing and developing good e-governance was presented in three stages of reviewing and identifying the requirements, establishment and development of good e-governance.
Volume 24, Issue 2 (3-2022)
Abstract
Extension and educational programs use various measures to advise farmers on adapting to climate change. Satisfaction with these programs is a tool to study their effectiveness. In this respect, studying the factors influencing satisfaction with extension and educational programs can help planners and policymakers of the agricultural sector in general, and agricultural extension in particular, to improve the quality of these programs. Therefore, the present paper explores the factors influencing satisfaction and loyalty in extension and educational programs. The statistical population was composed of all participants of these programs in Fars Province, Iran. A total of 150 participants was estimated as the sample size. Participants were selected through random sampling. Data collected from the participants were analyzed by structural equation modeling. The results showed that the research variables had optimal validity and reliability. The variables of appropriate extension packages and perceived value were among the most important factors dictating satisfaction with extension and educational programs. In addition to these two variables, other factors including image, emotions, perceived economic return, and tangibles of the educational programs had direct impacts on satisfaction and indirect impacts on loyalty to these programs. Research findings can help farmers to adapt to climate change.
Volume 24, Issue 3 (10-2020)
Abstract
Crises are always the hardest test for every management theory. There are few management theories that work in the face of severe crises. As a result, organizations and managers in practice, during major crises, suspend many of their functions, dimensions and tasks. Meanwhile, the field of decision-making has a special status, because this field can’t be closed at all. Accordingly, practical theories of decision making in crisis are one of the most essential needs of any organization in times of crisis. In this regard, we tried to explain the application of PANDA decision-making strategy in critical situations. To this end, the corona crisis was chosen as the focus area. The Corona crisis, as one of the most important human crises that is currently affecting the whole world, is the best option for this purpose. In order to narrow the scope of the research, the decisions of the National Anti-Corona Headquarters of Iran were selected as our cases. Therefore, multiple case study method was selected as the method of the present study. The results of this study show that the characteristics of consequentialism, multiple feedback, speed of action and systematic attitude are the four main characteristics of Panda method that make this method especially suitable for critical situations.
Volume 24, Issue 3 (5-2022)
Abstract
Pomegranate is a popular fruit, rich in antioxidants and minerals but sensitive to postharvest storage. The efficiency of 5 and 10 mM γ-Aminobutyric Acid (GABA) combined with 0.5% carnauba wax as edible coating was investigated on extending the cold storage life of pomegranate fruit (Cv. Malas Saveh) after 45 and 90 days. Coatings maintained fruit freshness, inhibited the chilling injury symptoms, reduced peel malondialdehyde formation (minimum of 0.74 nM g-1), reduced loss of aroma/taste, and increased aril antioxidant activity (maximum of 94.9%). Aril anthocyanin content was more stable in 5 mM GABA coated than uncoated fruits. However, the coatings caused more weight loss on 45th day (11.0% in 10 mM GABA and 8.3% in the control). This parameter was similar in coated and uncoated fruits after 90 days. Aril phenolic content in coated fruits was higher on 90th day but not on 45th day (maximum of 0.08 mg.100g-1 in the control on day 45). Aril lightness increased in the control sample on 45th day while coated fruits were more similar to harvest time. After 90 days, the control and treated samples were similar. The color scales (a*, b*, and Chroma) values of peels and arils declined by storage without any significant effects of coatings. Peel and aril Hue did not change by storage time or coatings. Results suggested some benefits of coatings for retaining the postharvest quality of pomegranate fruits.
Volume 24, Issue 4 (Winter 2024)
Abstract
Aim and Introduction
Today, with the expansion of globalization and increased economic competition, capital accumulation has been proposed as one of the main factors of the economic growth process of the countries, which can be provided through domestic or foreign sources. Meanwhile, inadequacy of internal resources and the need for high technical knowledge in some countries that seek economic growth have required a serious approach to this issue. Furthermore, countries with limited domestic resources are not able to expand exports and acquire shares from new markets, and they need stable resources to provide capital and their needs, among which attracting foreign capital is one of the economic solutions. Indirect foreign investment includes investments made by foreign natural and legal entities in the form of buying securities of a financial institution and company and providing them to the host country during a process. Due to the important role of foreign direct investment, the global market for attracting these funds has become really competitive. Such competition has been formed especially among developing countries due lack of financial resources on the one hand, and the need for achieving rapid development on the other. Therefore, it is crucilaly important to identify the factors affecting the flow of foreign direct investment. As a result, the aim of the present study is to investigate the relationship between foreign investment and crimes committed in 31 provinces of the country during 2001-2021 using panel data regression models and unit root stationarity tests of Levin, Lin and Chu, Im, Pesaran and Shin, Fisher and Fisher.
Methodology
According to the theoretical foundations of foreign direct investment and crime and the study conducted by Daniele and Marani in 2008, regression model (panel data) and static test have been considered to investigate the relationship between foreign direct investment and crime. In other words, in the estimation of regression models in the form of time series, it is critically important to check the stationarity of the variables, and for this purpose, Levin, Lin and Chu, Im, Pesaran and Shin, Fisher and Fisher tests were used in this study. The variables investigated in this study include foreign direct investment as a dependent variable and population variables, GDP per capita, industry index, degree of openness of the regional economy, infrastructure index and crime variable as an independent variable.
Findings
The results indicate that the test of the first model shows a negative relationship between foreign direct investment and crime, which is not statistically significant. In other words, with the increase in crime, the power to attract foreign direct investment in each province decreases. The results of the second model indicate that the logarithm of GDP per capita has a negative and significant effect on the entry of foreign direct investment. In other words, with the increase of GDP in each province, the amount of foreign direct investment attraction decreases. In the third model, in addition to the gross domestic product, the logarithm of the investment of exploitation licenses issued in each province as an industry index of each province has been entered into the model, which has a negative and significant effect on foreign direct investment. In the fourth model, the variable related to the country's infrastructure, which in this study is the amount of electricity subscribers of each province, has a positive and significant effect, and by entering the infrastructure variable, the effect of other variables is the same as before. The variable of the degree of openness of the economy in the fifth model shows a positive and significant effect on foreign direct investment, and it shows that the more suitable the country has for trade with other countries, the more the desire to invest in the country increases and the more foreign direct investment is attracted. GDP per capita variables and industry index have a negative and significant effect, and the infrastructure variable also has a positive and significant effect on foreign direct investment. In final model where the population variable is entered, the results indicate a negative and significant effect of the population on foreign direct investment. In other words, with the increase in population, the power to attract direct investment in each province decreases.
Discussion and Conclusion
The results obtained from the present study indicate that although, based on the data examined in this study, crimes have not had a significant effect on the attraction of foreign direct investment, but the negative effects of GDP per capita and the industry index indicate that despite Iran's capabilities, it requires official and long-term planning to provide the necessary ground for attracting foreign direct investments. It seems that a step can be taken in this direction by applying the reduction of restrictions in the field of commercial policies, especially the foundation through tariff and customs policies and application of protective laws and regulations
Today, with the expansion of globalization and increased economic competition, capital accumulation has been proposed as one of the main factors of the economic growth process of the countries, which can be provided through domestic or foreign sources. Meanwhile, inadequacy of internal resources and the need for high technical knowledge in some countries that seek economic growth have required a serious approach to this issue. Furthermore, countries with limited domestic resources are not able to expand exports and acquire shares from new markets, and they need stable resources to provide capital and their needs, among which attracting foreign capital is one of the economic solutions. Indirect foreign investment includes investments made by foreign natural and legal entities in the form of buying securities of a financial institution and company and providing them to the host country during a process. Due to the important role of foreign direct investment, the global market for attracting these funds has become really competitive. Such competition has been formed especially among developing countries due lack of financial resources on the one hand, and the need for achieving rapid development on the other. Therefore, it is crucilaly important to identify the factors affecting the flow of foreign direct investment. As a result, the aim of the present study is to investigate the relationship between foreign investment and crimes committed in 31 provinces of the country during 2001-2021 using panel data regression models and unit root stationarity tests of Levin, Lin and Chu, Im, Pesaran and Shin, Fisher and Fisher.
Methodology
According to the theoretical foundations of foreign direct investment and crime and the study conducted by Daniele and Marani in 2008, regression model (panel data) and static test have been considered to investigate the relationship between foreign direct investment and crime. In other words, in the estimation of regression models in the form of time series, it is critically important to check the stationarity of the variables, and for this purpose, Levin, Lin and Chu, Im, Pesaran and Shin, Fisher and Fisher tests were used in this study. The variables investigated in this study include foreign direct investment as a dependent variable and population variables, GDP per capita, industry index, degree of openness of the regional economy, infrastructure index and crime variable as an independent variable.
Findings
The results indicate that the test of the first model shows a negative relationship between foreign direct investment and crime, which is not statistically significant. In other words, with the increase in crime, the power to attract foreign direct investment in each province decreases. The results of the second model indicate that the logarithm of GDP per capita has a negative and significant effect on the entry of foreign direct investment. In other words, with the increase of GDP in each province, the amount of foreign direct investment attraction decreases. In the third model, in addition to the gross domestic product, the logarithm of the investment of exploitation licenses issued in each province as an industry index of each province has been entered into the model, which has a negative and significant effect on foreign direct investment. In the fourth model, the variable related to the country's infrastructure, which in this study is the amount of electricity subscribers of each province, has a positive and significant effect, and by entering the infrastructure variable, the effect of other variables is the same as before. The variable of the degree of openness of the economy in the fifth model shows a positive and significant effect on foreign direct investment, and it shows that the more suitable the country has for trade with other countries, the more the desire to invest in the country increases and the more foreign direct investment is attracted. GDP per capita variables and industry index have a negative and significant effect, and the infrastructure variable also has a positive and significant effect on foreign direct investment. In final model where the population variable is entered, the results indicate a negative and significant effect of the population on foreign direct investment. In other words, with the increase in population, the power to attract direct investment in each province decreases.
Discussion and Conclusion
The results obtained from the present study indicate that although, based on the data examined in this study, crimes have not had a significant effect on the attraction of foreign direct investment, but the negative effects of GDP per capita and the industry index indicate that despite Iran's capabilities, it requires official and long-term planning to provide the necessary ground for attracting foreign direct investments. It seems that a step can be taken in this direction by applying the reduction of restrictions in the field of commercial policies, especially the foundation through tariff and customs policies and application of protective laws and regulations
Volume 24, Issue 4 (Winter 2024)
Abstract
Aim and Introduction
The housing sector is one of the important economic sectors that, in addition to consumer demand, also faces demand from speculators due to its high capital return rate and low risk level. Speculators, motivated by the desire to profit from future price increases, refrain from offering their houses for sale, resulting in a housing vacancy. The presence of vacant houses reduces the housing supply and can lead to the formation of a housing price bubble. Imposing taxes on vacant houses is one of the government's tools to address this issue. The aim of this study is to examine the impact of taxes on vacant houses on the housing price bubble in the city of Shiraz.
Methodology
In this research, an agent-based model is used, considering four active agents in the housing market: sellers, buyers (including sellers and buyers with personal consumption and speculative motivations), developer, and real estate agencies, to investigate the dynamic processes of the housing market. To forecast the housing prices in Shiraz over an eight-year period, statistics and information by the beginning of 2022 have been incorporated into the model, and three different percentages of speculative buyers, including 30%, 50%, and 70% of the total buyers, along with different tax rates of 10%, 15%, 20%, and 25% have been considered.
Findings
The results of the research show that by applying a tax rate of 10%, if 70% of buyers are speculators, the highest growth rate of the housing price bubble was observed; that the decreasing growth rate was equal to 18%, that is, with application of tax on empty houses, the housing price bubble of Shiraz city in 2022 to the end of 2031 decreased by almost 19%, and after that the application of the tax rate of 15% in these conditions was approximately 17% which reduced the housing price bubble. But when the number of regular buyers is more than speculative buyers (30% of buyers are speculative), the application of different tax rates on vacant houses shows the least reduction effect on the housing price bubble. Therefore, when 70% of the buyers in the market are present in the market with the motive of personal consumption, the number of transactions is low. Since ordinary buyers will re-enter the market with a slight probability, and the majority of transactions are made by the 30% of buyers who are speculative, so applying the tax on vacant houses in the first year will cause a number of speculater to leave the market and the number of transactions will be less than before the tax was applied. In fact, mobilisation of the current stock of housing due to the tax may not have been high enough to affect prices which is consistent with Sego (2019).
Furthermore, the results indicate that increasing the tax rate on vacant houses does not necessarily lead to a further reduction of housing price bubble. When more than half of the housing market is in the hands of speculators, their power in transactions would be greater, and the increase in tax rate in the form of an increase in price will intensify the housing price bubble which could mean more transactions between traders. In fact, traders add tax to the price of the property, and increasing tax rates, in return worsens the bubble. So, here selecting the optimal tax rate becomes critically important. When less than half of the housing market is in the hands of speculators, the power of speculators will decrease as a result, which leads to further weakening of the price bubble. However, to a lesser extent when more than half of the market is in the hands of speculators, the price bubble will decrease.
Discussion and Conclusion
The research results indicate that the implementation of different tax rates, despite varying numbers of speculators, can lead to a reduction in the housing price bubble in the city of Shiraz, although the effectiveness may vary under different conditions. Moreover, it can create an appropriate income for the government, which can reduce the class gap by allocating and optimally directing the resulting resources towards the supply of housing for low-income groups. But the government should be careful in choosing the tax rate. It is necessary to set the tax rate on empty houses in such a way that renting the house or offering it in the market is more economical than keeping it empty by traders. In addition to the tax rate, choosing the tax base is also crucial. As mentioned in the text of the research, some countries consider the value of the property as the tax base instead of the rental income, or a fixed annual tax is collected
The housing sector is one of the important economic sectors that, in addition to consumer demand, also faces demand from speculators due to its high capital return rate and low risk level. Speculators, motivated by the desire to profit from future price increases, refrain from offering their houses for sale, resulting in a housing vacancy. The presence of vacant houses reduces the housing supply and can lead to the formation of a housing price bubble. Imposing taxes on vacant houses is one of the government's tools to address this issue. The aim of this study is to examine the impact of taxes on vacant houses on the housing price bubble in the city of Shiraz.
Methodology
In this research, an agent-based model is used, considering four active agents in the housing market: sellers, buyers (including sellers and buyers with personal consumption and speculative motivations), developer, and real estate agencies, to investigate the dynamic processes of the housing market. To forecast the housing prices in Shiraz over an eight-year period, statistics and information by the beginning of 2022 have been incorporated into the model, and three different percentages of speculative buyers, including 30%, 50%, and 70% of the total buyers, along with different tax rates of 10%, 15%, 20%, and 25% have been considered.
Findings
The results of the research show that by applying a tax rate of 10%, if 70% of buyers are speculators, the highest growth rate of the housing price bubble was observed; that the decreasing growth rate was equal to 18%, that is, with application of tax on empty houses, the housing price bubble of Shiraz city in 2022 to the end of 2031 decreased by almost 19%, and after that the application of the tax rate of 15% in these conditions was approximately 17% which reduced the housing price bubble. But when the number of regular buyers is more than speculative buyers (30% of buyers are speculative), the application of different tax rates on vacant houses shows the least reduction effect on the housing price bubble. Therefore, when 70% of the buyers in the market are present in the market with the motive of personal consumption, the number of transactions is low. Since ordinary buyers will re-enter the market with a slight probability, and the majority of transactions are made by the 30% of buyers who are speculative, so applying the tax on vacant houses in the first year will cause a number of speculater to leave the market and the number of transactions will be less than before the tax was applied. In fact, mobilisation of the current stock of housing due to the tax may not have been high enough to affect prices which is consistent with Sego (2019).
Furthermore, the results indicate that increasing the tax rate on vacant houses does not necessarily lead to a further reduction of housing price bubble. When more than half of the housing market is in the hands of speculators, their power in transactions would be greater, and the increase in tax rate in the form of an increase in price will intensify the housing price bubble which could mean more transactions between traders. In fact, traders add tax to the price of the property, and increasing tax rates, in return worsens the bubble. So, here selecting the optimal tax rate becomes critically important. When less than half of the housing market is in the hands of speculators, the power of speculators will decrease as a result, which leads to further weakening of the price bubble. However, to a lesser extent when more than half of the market is in the hands of speculators, the price bubble will decrease.
Discussion and Conclusion
The research results indicate that the implementation of different tax rates, despite varying numbers of speculators, can lead to a reduction in the housing price bubble in the city of Shiraz, although the effectiveness may vary under different conditions. Moreover, it can create an appropriate income for the government, which can reduce the class gap by allocating and optimally directing the resulting resources towards the supply of housing for low-income groups. But the government should be careful in choosing the tax rate. It is necessary to set the tax rate on empty houses in such a way that renting the house or offering it in the market is more economical than keeping it empty by traders. In addition to the tax rate, choosing the tax base is also crucial. As mentioned in the text of the research, some countries consider the value of the property as the tax base instead of the rental income, or a fixed annual tax is collected
Volume 24, Issue 5 (May 2024)
Abstract
The main approach in the study of fluid flow instabilities is the theory of linear stability, which is based on linearizing the governing equations and finding unstable eigenvalues. In many flows, like shear flows, the results of linear stability theory fail to match most experiments. In a linear system, even if all the eigenvalues are stable, the perturbations can lead to instability, if the eigenfunctions are not orthogonal. The transient features of these non-normal dynamical systems, can be described with low-dimensional structures, i.e. a few modes. It is possible to suppress the asymptotic and transient growth by identification of time-dependent modes. In this paper, a method of order reduction based on optimally time-dependent modes has been implemented. This method identifies the growth behavior of disturbances in short and long times. Also, a control algorithm based on the above method has been implemented to stabilize the growth of disturbances. The DNS solution of the flow and the implementation of the reduction and control algorithms is based on the NEKTAR++ open-source solver. At first problem, to validate the solution method, the order reduction and control algorithm has been implemented on the flow over a cylinder with Re=50. At second problem, for the first time, the control algorithm is implemented on the flow over a cylinder subjected to persistent time-varying disturbances. The results show that by applying a control force, the Von-Karman vortices are stabilized and a constant lift is obtained and body vibrations are cancelled.
Volume 25, Issue 4 (Winter 2021)
Abstract
As a confrontation tool, economic sanctions are applied by the developed states against the developing states in order to make the state under sanctions adjust to demands imposed by the states sponsoring sanctions. The sanctions produce a variety of economic, social, legal and other effects, including an effect on contractual commitments. Whereas no specific law has been devised with regard to the effect of international sanctions on contractual commitments in Iran’s legal system, the issue has been addressed in international arbitration and judicial procedures of other countries. The main question addressed in this study, is that what approach Iran’s legal system and international trade law adopt towards the effect of economic sanctions on commitments. The findings of the present study note considerable differences. To begin with, in international trade law system, the effects are examined, using three doctrines of hardship, frustration and force majeure, while no particular approach is observed in Iran’s legal system in this regard. Secondly, in international trade law system, a single approach, considering economic sanctions as a force majeure, hardship or frustrating event, is not observed. However, most procedures tend toward the frustration doctrine. In the meantime, Iran’s judicial systems for the most part seems to gravitate towards considering international sanctions as force majeure.
Volume 26, Issue 1 (1-2024)
Abstract
The present study was conducted to investigate the effects of two concentrations of Aloe vera gel (7.5 and 15%) on quantitative and qualitative characteristics of lime during storage time (20, 40, and 60 days). The study was performed as a factorial experiment in a completely randomized design with four replications. After dipping (5 minutes) and drying, the fruits were packaged in low-density polyethylene containers and transferred to cold storage at 4±1°C and 85±2% relative humidity. The results showed a decrease in fruit sourness and aroma and an increase in fruit bitterness during storage. The highest rate of chilling injury and decay belonged to the control. Aloe vera gel 15% had the lowest fruit bitterness (30%), decay, and malondialdehyde compared to the control on day 60 of storage. The Aloe vera gel enhanced peroxidase activity as an antioxidant enzyme and decreased defense-related enzymes such as phenylalanine ammonia-lyase activity. The maximum vitamin C was related to Aloe vera gel 15%. According to the results, Aloe vera gel, could not effectively control weight loss and firmness. During 60 days of storage, compared to the control, Aloe vera gel 15% increased Chroma index (2.07%) and vitamin C (26.37%), and prevented decay (100%), chilling injury (25.75%), bitterness (42.85%), and malondialdehyde (35.80%) of lime fruit.
Assessment of the Impacts of Climate Change on Soybean Yield and Water Requirement Using Crop Models
Volume 26, Issue 3 (5-2024)
Abstract
Climate change can have significant impacts on crop growth, yield, water requirement and, consequently, crop water productivity. In this study, the effect of climate change under RCP2.6, RCP4.5, and RCP8.5 projection scenarios of the CanESM2 model on soybean yield and water requirement was investigated in Kermanshah, west of Iran. Crop growth was simulated using crop growth simulation models (DSSAT and AquaCrop) based on historical (1985-2015) and projected (2025-2064) weather data. Using the AquaCrop model in RCP2.6, RCP4.5, and RCP8.5 scenarios, the average increase in seasonal crop evapotranspiration (ETc) was estimated to be 9.4, 11, and 14.9%, respectively. The results of the DSSAT model showed 4.1, 8.5, and 12.1% increase in seasonal ETc under the RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. Based on the AquaCrop and DSSAT models, soybean yield decreases by 5.3, 3.7, and 2% and by 5.7, 4.8, and 1.6% for the RCP8.5, RCP4.5, and RCP2.6 scenarios, respectively. The results also show a decrease in crop water productivity under climate change scenarios as a result of increased ETc and reduced grain yield. According to AquaCrop and DSSAT models, the maximum daily ETc that should be used for the design of irrigation systems will increase by 11.5 and 10.2%, respectively.
Volume 26, Issue 4 (7-2024)
Abstract
The tomato leafminer, Tuta absoluta is a devastating invasive pest that poses a serious threat to tomato crops worldwide. Its extensive global dispersion serves its capacity to adapt to variations in climate conditions. In this context, the pupa is the most resistant stage to prolonged exposure to cold temperatures. Therefore, indicators of cold resistance were studied in overwintering pupae collected from the field and pupae reared under two constant conditions, high temperature, and long day (25°C, 16:8 L:D and 65±5% RH), and low temperature and short day (15°C, 13:11 L:D and 65±5% RH). The results show that the super cooling point (SCP) significantly decreased in December (-20.5±1.2°C) and January (-20.26±0.78°C) with a decrease in temperature. In the laboratory, the decrease in temperature and photoperiod increased the tolerance of pupae to subzero temperatures. Lethal Temperature 50 (LT50) and LT90 of pupae collected in the field were recorded at -13.70 to -10.23°C and -18.73 to -15.37°C, respectively. A comparison of lethal temperatures with the lowest ambient temperature in December and January indicated that T. absoluta has a high overwintering potential in Karaj, Alborz Province, Iran, and can easily survive cold winters.
Volume 26, Issue 5 (9-2024)
Abstract
The present study investigated the effects of five Iranian male palm pollen grains as pollen sources on the fruit quality of two cultivars, ‘Barhee’ and ‘Piyarom’ (offshoot-derived and tissue culture-derived). The biochemical and enzymatic properties of fruit dates at the Tamar stage (full maturity) enabled the evaluation of pollen source effects on fruit quality. The research location was Jahrom Research Station, Fars Province, Iran, from 2018 to 2019. The pollen sources were genotypes ‘7001’ (control), ‘7005’, ‘7013’, ‘7030’, and ‘B11’. Pollinated with 7013 pollen, Offshoot-erived (OFS) trees of the ‘Barhee’ cultivar had the highest fruit flesh pH (7.07). In contrast, the lowest pH value (5.84) occurred in fruits of Tissue Culture-Derived (TCD) trees of the ‘Piyarom’ pollinated with the 7030. In the OFS ‘Piyarom’ the pollen source 7001 caused the highest fruit TSS (68.83%). When pollinated with the B11, ‘Barhee’ had the lowest fruit TSS (44.90%). In TCD ‘Piyarom’ trees, the 7030 pollen caused the highest TSS (62.53%). By receiving pollen from B11, the ‘Barhee’ produced fruits with the lowest TSS (44.23%). Regardless of being OFS or TCD and of the pollen source, on average, ‘Barhee’ produced fruits with more moisture content than fruits of the ‘Piyarom’. In OFS ‘Piyarom’ trees, pollen from the 7030 caused the highest Fruit Dry Matter (FDM) (87.40%), whereas the ‘Barhee’ pollinated with the 7001 produced fruits with the lowest FDM (67.15%). In TCD ‘Piyarom’ palms, pollen from the 7030 caused the highest FDM (85.19%), compared to the ‘Barhee’ pollinated with the 7013, which showed the lowest FDM (67.87%). Pollen from the 7030 caused the highest total sugar content in the fruits of OFS and TCD ‘Piyarom’ trees. The fruits of OFS ‘Piyarom’ trees had more Fe and Polyphenol Oxidase (PPO) activity than TCD ‘Piyarom’ trees.
Volume 27, Issue 4 (Winter 2023)
Abstract
Historical tourism is one of the biggest sources of economic development in any region and its rapid growth accompanies abundant changes. As such, it is necessary to value tourism attractions using appropriate methods in order to express the importance of historical tourism as well as convert it into monetary values. In the present study, the recreational value of the largest museum in the southeastern Iran located in Sistan and Baluchistan province was estimated using the conditional valuation method whereas the Logistic regression method was taken into account to investigate the factors affecting the willingness of visitors to pay for the improvement and protection of this museum. For this purpose, first, the sample size was determined based on Cochran's method, and then the data were collected through a questionnaire and face-to-face interviews. The results showed that the variables such as "occupation", "income", "visited season" and "maximum offered amount” have had a significant effect on people's willingness to pay, but the variables like "age", "gender", "marital status", "education”, "number of household members", "conveyance", "being native or non-native", "main purpose of visit" and "attractiveness of the area" have had no significant effect. Also, based on the calculations, the average inclination of each visitor to pay in order to protect and improve the condition of the museum of Southeast Iran was 100,950 Rials per month, and its annual recreational value was estimated to 4,554,860 Rials, which showed the high importance of this museum for visitors.
Volume 29, Issue 3 (9-2022)
Abstract
Stylistics is one of the braches of literary criticism that particularly focuses on the data of linguistics and rhetoric and deals with its text and structure to reveal inherent aesthetics in it and show the reader expressive patterns, leading to distinguish the works of writers. Sheikh Ahmad Al-Waeli is one of the contemporary poets who took an active style in his political poems, especially “Hadith Palestine”. He talks about the will of the people of this land in particular and the Arabs in general to defend their usurped rights. This study aims to analyze the ode at two levels i.e. semantic and rhetorical by taking into account the descriptive-analytical method, to reveal its inherent connotations and reach its wonderful aesthetics. The results of this study show that the poet employs tandem at the semantic level and contrast to understand ideas about the land of Palestine and Palestinian uniqueness and increasing sense of patriotism. He applauds the Palestinian fighters who did not leave their resistance on the occupied land. In terms of rhetoric, the poet uses verbal repetition in a special way to alert the addressee that the concept presented through repetition needs more caution and awareness. The dialogue that takes place in the ode by asking questions from a child and answering by his father, prepares the reader to reflect about the right of the Palestinians to demand and the invalidity of the occupiers. Although the father, while answering to the child, expects the good and success in the future for his country, to not forget the depression weighing on his shoulders, which is racist and hateful on the part of the Zionists who try to promote it from time to time that the Arabs are not equal to them.