In this paper harmonic resonance analysis of the grid comprising wind power plants (WPPs) with pe... more In this paper harmonic resonance analysis of the grid comprising wind power plants (WPPs) with permanent magnet synchronous generators (PMSGs) is presented. Usually, Norton equivalent circuit is used as the wind turbine (WT) model for harmonic resonance studies, in which, WTs are simply modeled as ideal current and voltage sources and impacts of converters controls on the WTs output impedances are neglected. This paper deals with the harmonic resonance analysis of study WPP system taking the impacts of converters controls, and current and voltage measurement filters into account. In this way, harmonic impedance models of the WTs are presented for simple and detailed cases, and then WT harmonic impedance is extracted for the mentioned cases. Next, results of frequency scan and harmonic mode resonance analyses for different cases are given and compared, and then effects of the current and voltage measurements filters and WT converter control on harmonic resonance analysis of the study WPP system are presented. It is shown that increasing the bandwidth of the grid-side converter current control loop can not shift the resonant frequencies, but enhances the system damping, and consequently reduces the driving point impedances in the resonant frequencies.
This paper, rst, deals with the analytical controller design of wind turbines with variable rotor... more This paper, rst, deals with the analytical controller design of wind turbines with variable rotor-resistance control. Wind turbines with variable rotor-resistance control, known as Limited Variable Speed Wind Turbine (LVS-WT), provide a limited variation of the generator speed. In the LVS-WT, the rotor current and, consequently, the output power can be controlled by varying the rotor resistance. Then, modal and small signal analyses of the wind turbine are examined. It is found that for certain values of shaft sti ness, frequency of the mechanical modes coincides with the triple oscillation frequency appeared due to tower shadow e ects. This in turn results in resonance phenomena magnifying the uctuation of the generator power and electromagnetic torque. Next, the paper evaluates the impact of aerodynamic torque uctuations on the dynamic response of the LVS-WT. In this way, analytical expressions for the uctuations of the stator voltage and current, electromagnetic torque, and generator active power are proposed. These uctuations arise because of the aerodynamic torque and rotor speed perturbations. The paper also investigates the e ects of shaft sti ness, slope of power-slip curve, and rotor resistance on the wind turbine response. At the end, time domain simulations verify the results of theoretical analyses.
Background: Effective malaria control strategies require an accurate understanding of the epidemi... more Background: Effective malaria control strategies require an accurate understanding of the epidemiology of locally transmitted Plasmodium species. Emerging evidence indicates that migrants from malaria endemic regions are at risk of delayed presentation of Plasmodium spp. and malaria infection. Cases Report: We reported a case of P. vivax malaria occurring after arrival in Iran. Patient was originally from Iraq. A 48-year-old male patient who was hospitalized with fever attacks, chills, and headache after arriving from Iraq to Tehran. Conclusion: In this patient, new prevention and screening strategies should be studied and blood safety policies adapted. Thus, ultimate elimination of malaria in Iran will require national malaria control program to adopt policy and practice aimed at all human species of malaria since neighbor country are still face to problem to control of malaria.
The system under study in this paper is a real 710 kW DFIG based wind turbine installed in the bi... more The system under study in this paper is a real 710 kW DFIG based wind turbine installed in the binalood site. Based on the measurements and observations of the turbine, at high wind speeds, electromechanical oscillations with frequency of 2 Hz apear on the mechanical system leading to turbine vibration. Control of the wind turbine is carried out based on the power control through a predefined power-speed curve provided by the wind turbine manufacture. The purpose of this paper is to find out the nature and reason of the above mentioned electromechanical oscillations. Hence, the paper first deals with the power control design based on the corresponding power-speed curve. Then, mechanical modes of the system under different operating conditions and wind speeds are extracted. It is shown that at some operating points, low frequency oscillations with frequency of 2 Hz appear on the generator power, generator speed and shaft torsional torque. Next, for improving the damping of the torsio...
Background: Paying for the global surgery is one of the prospective payment methods in which serv... more Background: Paying for the global surgery is one of the prospective payment methods in which service providers receive their service costs according to a preset table. In this method, payment is based on patients' treatment not in terms of any remedial action. Therefore, it reduces the motivation of rendering unreasonable service. However, its weak point is making simple diseases complex as well as reducing consumption of resources for patients and etc. Since surgeries are considered as costly items in Iran's insurance system, the present study targeted at investigating the hoteling cost of global surgery in Isfahan public hospitals. Methods: This descriptive and Applied research has investigated the difference between real hoteling cost of 60 global surgeries and the amount of paid hoteling in global plan in Isfahan public hospitals in 2012. The real hoteling cost of the global surgery (real rate of patients' hospitalization) was collected through Hospital Information S...
Purpose Echinococcosis is one of the most important parasitic zoonotic diseases around the world.... more Purpose Echinococcosis is one of the most important parasitic zoonotic diseases around the world. Echinococcus granulosus is the most widespread species of the genus Echinococcus that can develop cysts in different parts of the body. We tried to present a case of pulmonary cystic echinococcosis. Methods Here, we report a rare case of two ruptured and intact cysts in a 54-year-old woman with weakness, lethargy, body pain, stomachache, dizziness, and vision problems. Results According to the patient's manifestations and imaging findings, besides the COVID-19 pandemic, she was suspected of having COVID-19 and tuberculosis. However, when the aspirated sample was stained, hooklets of E. granulosus were observed. Surgical removal and chemotherapy were used for treatment. Conclusion Treatment of pulmonary cystic echinococcosis is based on surgery, but, along with it, the chemotherapy makes a better prognosis.
Objective(s): Rapid healing of cutaneous leishmaniasis as one of the most important parasitic dis... more Objective(s): Rapid healing of cutaneous leishmaniasis as one of the most important parasitic diseases leads to the decrease of scars and prevention of a great threat to the looks of the affected people. Today, the use of nano-scaffolds is rapidly increasing in tissue engineering and regenerative medicine with structures similar to the target tissue. Chitosan (CS) is a bioactive polymer with antimicrobial and accelerating features of healing wounds, which is commonly used in biomedicine. This study aimed to investigate the effects of CS/polyethylene oxide (PEO)/berberine (BBR) nanofibers on the experimental ulcers of Leishmania major in BALB/c mice. Materials and Methods: CS/PEO/BBR nanofibers were prepared by the electrospinning method, and their morphology was examined by SEM, TEM, and AFM. Then, water absorption, stability, biocompatibility, porosity, and drug release from nano-scaffolds were explored. Afterward, 28 BALB/c mice infected with the parasite were randomly divided int...
With increase of wind power penetrations into the power system, attention to power quality become... more With increase of wind power penetrations into the power system, attention to power quality becomes an important issue. Important aspects of power quality are flicker and harmonics. There are numerous factors that affect on flicker emission and power oscillations of grid-connected wind turbines for example wind characteristics (mean wind speed, tower shadow and wind shear effects and type of used wind turbine) and the grid conditions (short circuit capacity ratio and grid impedance angle) and type of the maximum power point tracking. In the present paper, performances of two maximum power point tracking methods (TSR and OTC) in fluctuations emission are evaluated and fluctuations caused by the tower shadow are then reduced by adding filter when the best MPPT method and grid conditions are selected. All aerodynamic, mechanical and electrical aspects of a wind farm connected to the grid are modeled using FAST and MATLAB/SIMULINK. The simulation results are given and they show well the ...
Objective(s): Various methods for repairing bone defects are presented. Cell therapy is one of th... more Objective(s): Various methods for repairing bone defects are presented. Cell therapy is one of these methods. Bone marrow stromal cells (BMSCs) seem to be suitable for this purpose. On the other hand, lots of biomaterials are used to improve and repair the defect in the body, so in this study we tried to produce a similar structure to the bone by the chitosan and hydroxyapatite. Materials and Methods: In this study, the solution of chitosan-nanohydroxyapatite-polyethylene oxide (PEO) Nanofibers was produced by electrospinning method, and then the BMSCs were cultured on this solution. A piece of chitosan-nanohydroxyapatite Nanofibers with BMSCs was placed in a hole with the diameter of 1 mm at the distal epiphysis of the rat femur. Then the biomechanical and radiographic studies were performed. Results: Biomechanical testing results showed that bone strength was significantly higher in the Nanofiber/BMSCs group in comparison with control group. Also the bone strength in nanofiber/BMS...
International journal of humanities and social sciences, 2016
During the last two decades, many higher education systems in the world has attempted to evaluate... more During the last two decades, many higher education systems in the world has attempted to evaluate and improve the quality of education, research and services at the university and higher education level. Countries which have been successful in these attempts have initiated continuous evaluation and applied internal evaluation as a basis for promoting quality culture. Quality assurance as a comprehensive term encompasses all policies, processes and actions maintaining and developing higher education quality. Quality assurance emphasizes on external goals of evaluation, one of which is to assure learners, public and government that each unit, department, program or institution manages its quality. Thus quality assurance focuses on accountability. In Iran, also, implementation of continuous evaluation projects started in 1996.Then; attempts were made to institutionalize departmental internal evaluation at the university level. This article describes importance of Quality Assurance and ...
Australian journal of basic and applied sciences, 2011
Arsanjan city having green forests and exposure Has great potential to attract tourists Zagross b... more Arsanjan city having green forests and exposure Has great potential to attract tourists Zagross beam is. One of the places in this city forest green Bonab, so in effect each of these factors on willingness to pay and the estimated value of the recreational forest park is Bonab. And for this study were 255 visitors of the study area were selected by simple random sampling, was completed. Visitors of the Logit model to estimate the willingness to pay based on maximum likelihood method was used. The results show that the average willingness to pay for the value of tourist visitors to the park, each visit is 10193.68 Rials. The results also show that variables such as income and educational level of visitors that are statistically significant at one percent, the most important factors affecting the WTP of visitors are from Forest Park Bonab. The next factor to influence the environmental quality of the visitors are WTP, so the statistic is significant at the 5% level. Worth visiting the...
One of the environmental problems in the past two decades has been raising trend of global warmin... more One of the environmental problems in the past two decades has been raising trend of global warming and climate change resulting in destruction and environmental damage. This damage caused by a combination of factors such as population growth, economic growth, international trade and production activities, because these activities increased energy consumption in various economics sectors. The main purpose of this study was to examine the dynamic causal relationship between carbon dioxide diffusion (pollution index), energy consumption, per capita income, foreign trade and GDP of agriculture sector in Iran in 1983-2007. By using a ARDL method and error correction model (ECM), the long run and short-run relationship between variables was evaluated. Results showed a relationship between CO2 diffusion with energy consumption, per capita income and foreign trade. Economic
Objective(s): Design and construction of biocompatible and biodegradable scaffolds are among the ... more Objective(s): Design and construction of biocompatible and biodegradable scaffolds are among the main goals of tissue engineering. Recently, use of nano-hydroxyapatite as a bioactive bioceramic agent with high similarity to the mineral phase of the human bone tissue, in combination with biodegradable polymers and implant coatings has attracted the attention of researchers in the field of biomaterial sciences. The present study aimed to assess the differentiation of bone marrow stromal cells (BMSCs) in osteoblast-like cells on the chitosan/polyethylene oxide (PEO)/nano-hydroxyapatite scaffold in mature rats.Materials and Methods: Chitosan and PEO solution with the weight ratio of 80:20 and 70:30 were prepared, and 2% weight of nano-hydroxyapatite was added. Nanofibers were prepared using the electrospinning method, and the morphology was studied using scanning electron microscopy (SEM). Afterwards, the BMSCs of mature rats were cultured on nanofibers and differentiated by adding a di...
Wind turbine-generators shaft is relatively soft and wind turbine mechanical systems is usually r... more Wind turbine-generators shaft is relatively soft and wind turbine mechanical systems is usually represented as two mass model. Two mass model contains torsional oscillatory modes that may be excited under wind speed variations and grid fault conditions. In this state, torsional oscillations may appear on the output responses of the wind turbine-generator. PMSG based WTs include two converters: machine side converter (MSC) and grid side converter (GSC). The main function of the GSC is the dc-link voltage regulation. Also, the MSC is used to control the generator speed or active power, and thus the control of the generator is mainly carried out by the MSC. There are different strategies for the control of MSC. The purpose of this paper is to study different control strategies of the MSC in the PMSG based WTs. These control strategies include turbine-generator control in speed control mode, power control mode or optimum tip speed ratio mode. Then, performance of the WT by using the men...
Toxoplasma gondii is an intracellular parasite that has been associated with several mental disor... more Toxoplasma gondii is an intracellular parasite that has been associated with several mental disorders. It usually causes an inapparent primary infection. Found worldwide, T. gondii is capable of infecting virtually all warm-blooded animals.1-3Schizophrenia is a neurological disorder characterized with long-term and devastating neuropsychological problems, usually presenting in adolescents or young adults. The disease affects almost 1.1% of the global population including all races and ethnic groups with an equal prevalence in both sexes.1 T. gondii seroprevalence is strongly associated with 12-month generalized anxiety disorder but not with other anxiety, depressive, or alcohol-related disorders. Because of the intracellular nature of some parasites, their treatment and development of new drugs is a major challenge for scientists.4 Recently, the use of nanoparticles and nano-scaffolds has suggested for the treatment of parasitic diseases, although limited research has been done in t...
The system under study in this paper is a real 710 kW DFIG based wind turbine installed in the bi... more The system under study in this paper is a real 710 kW DFIG based wind turbine installed in the binalood site. Based on the measurements and observations of the turbine, at high wind speeds, electromechanical oscillations with frequency of 2 Hz apear on the mechanical system leading to turbine vibration. Control of the wind turbine is carried out based on the power control through a predefined power-speed curve provided by the wind turbine manufacture. The purpose of this paper is to find out the nature and reason of the above mentioned electromechanical oscillations. Hence, the paper first deals with the power control design based on the corresponding power-speed curve. Then, mechanical modes of the system under different operating conditions and wind speeds are extracted. It is shown that at some operating points, low frequency oscillations with frequency of 2 Hz appear on the generator power, generator speed and shaft torsional torque. Next, for improving the damping of the torsional modes, an auxiliary stabilizer control, known as torsional oscillations stabilizer (TOS), is proposed. At the end, simulation results for the system under study are presented.
Background: Leishmaniasis is the most important parasitic disease in Iran and is the third highes... more Background: Leishmaniasis is the most important parasitic disease in Iran and is the third highest rate of rural cutaneous leishmaniasis in the world. Chitosan-polyethylene oxide nanocomposite fibers can be a suitable replacement for ordinary bandages. For the first time, in the absence of any published reports, the present in vitro study aimed to evaluate the anti-leishmanial effects of chitosan (CS)-polyethylene oxide (PEO)-berberine nanofibers on Leishmania major. Methods: The present experimental study was conducted in 2018 in Tehran, Iran. The CS-PEO nanofibers containing berberine, as a natural anti-parasitic agent, were prepared using the electrospinning technique. Biocompatibility and fibroblast proliferation on nanofibers were investigated. In addition, the anti-leishmanial activity of CS-PEO nanofibers in both the promastigote and amastigote stages of Leishmania major was evaluated after parasite vital staining and MTT assay and compared to a control group. Statistical ana...
Hematobium species of this parasite tends to bladder and mesenteric arteries and it causes lesion... more Hematobium species of this parasite tends to bladder and mesenteric arteries and it causes lesions in the bladder wall, urethra, and renal tubes. A 25-year-old man living in Tehran (a non-endemic and very rare area for schistosoma) suffers from symptoms such as hematuria with suprapubic pain, dysuria, fever, nausea and vomiting. Urine analysis showed a lot of red blood cells, after using cystoscopy of the area and receiving a bladder biopsy, a definitive diagnosis of schistosomiasis was made and after determining the extent of damage to the urinary tract, appropriate treatment with surgery and praziquantel (40 mg/kg) were prescribed.
In this paper harmonic resonance analysis of the grid comprising wind power plants (WPPs) with pe... more In this paper harmonic resonance analysis of the grid comprising wind power plants (WPPs) with permanent magnet synchronous generators (PMSGs) is presented. Usually, Norton equivalent circuit is used as the wind turbine (WT) model for harmonic resonance studies, in which, WTs are simply modeled as ideal current and voltage sources and impacts of converters controls on the WTs output impedances are neglected. This paper deals with the harmonic resonance analysis of study WPP system taking the impacts of converters controls, and current and voltage measurement filters into account. In this way, harmonic impedance models of the WTs are presented for simple and detailed cases, and then WT harmonic impedance is extracted for the mentioned cases. Next, results of frequency scan and harmonic mode resonance analyses for different cases are given and compared, and then effects of the current and voltage measurements filters and WT converter control on harmonic resonance analysis of the study WPP system are presented. It is shown that increasing the bandwidth of the grid-side converter current control loop can not shift the resonant frequencies, but enhances the system damping, and consequently reduces the driving point impedances in the resonant frequencies.
This paper, rst, deals with the analytical controller design of wind turbines with variable rotor... more This paper, rst, deals with the analytical controller design of wind turbines with variable rotor-resistance control. Wind turbines with variable rotor-resistance control, known as Limited Variable Speed Wind Turbine (LVS-WT), provide a limited variation of the generator speed. In the LVS-WT, the rotor current and, consequently, the output power can be controlled by varying the rotor resistance. Then, modal and small signal analyses of the wind turbine are examined. It is found that for certain values of shaft sti ness, frequency of the mechanical modes coincides with the triple oscillation frequency appeared due to tower shadow e ects. This in turn results in resonance phenomena magnifying the uctuation of the generator power and electromagnetic torque. Next, the paper evaluates the impact of aerodynamic torque uctuations on the dynamic response of the LVS-WT. In this way, analytical expressions for the uctuations of the stator voltage and current, electromagnetic torque, and generator active power are proposed. These uctuations arise because of the aerodynamic torque and rotor speed perturbations. The paper also investigates the e ects of shaft sti ness, slope of power-slip curve, and rotor resistance on the wind turbine response. At the end, time domain simulations verify the results of theoretical analyses.
Background: Effective malaria control strategies require an accurate understanding of the epidemi... more Background: Effective malaria control strategies require an accurate understanding of the epidemiology of locally transmitted Plasmodium species. Emerging evidence indicates that migrants from malaria endemic regions are at risk of delayed presentation of Plasmodium spp. and malaria infection. Cases Report: We reported a case of P. vivax malaria occurring after arrival in Iran. Patient was originally from Iraq. A 48-year-old male patient who was hospitalized with fever attacks, chills, and headache after arriving from Iraq to Tehran. Conclusion: In this patient, new prevention and screening strategies should be studied and blood safety policies adapted. Thus, ultimate elimination of malaria in Iran will require national malaria control program to adopt policy and practice aimed at all human species of malaria since neighbor country are still face to problem to control of malaria.
The system under study in this paper is a real 710 kW DFIG based wind turbine installed in the bi... more The system under study in this paper is a real 710 kW DFIG based wind turbine installed in the binalood site. Based on the measurements and observations of the turbine, at high wind speeds, electromechanical oscillations with frequency of 2 Hz apear on the mechanical system leading to turbine vibration. Control of the wind turbine is carried out based on the power control through a predefined power-speed curve provided by the wind turbine manufacture. The purpose of this paper is to find out the nature and reason of the above mentioned electromechanical oscillations. Hence, the paper first deals with the power control design based on the corresponding power-speed curve. Then, mechanical modes of the system under different operating conditions and wind speeds are extracted. It is shown that at some operating points, low frequency oscillations with frequency of 2 Hz appear on the generator power, generator speed and shaft torsional torque. Next, for improving the damping of the torsio...
Background: Paying for the global surgery is one of the prospective payment methods in which serv... more Background: Paying for the global surgery is one of the prospective payment methods in which service providers receive their service costs according to a preset table. In this method, payment is based on patients' treatment not in terms of any remedial action. Therefore, it reduces the motivation of rendering unreasonable service. However, its weak point is making simple diseases complex as well as reducing consumption of resources for patients and etc. Since surgeries are considered as costly items in Iran's insurance system, the present study targeted at investigating the hoteling cost of global surgery in Isfahan public hospitals. Methods: This descriptive and Applied research has investigated the difference between real hoteling cost of 60 global surgeries and the amount of paid hoteling in global plan in Isfahan public hospitals in 2012. The real hoteling cost of the global surgery (real rate of patients' hospitalization) was collected through Hospital Information S...
Purpose Echinococcosis is one of the most important parasitic zoonotic diseases around the world.... more Purpose Echinococcosis is one of the most important parasitic zoonotic diseases around the world. Echinococcus granulosus is the most widespread species of the genus Echinococcus that can develop cysts in different parts of the body. We tried to present a case of pulmonary cystic echinococcosis. Methods Here, we report a rare case of two ruptured and intact cysts in a 54-year-old woman with weakness, lethargy, body pain, stomachache, dizziness, and vision problems. Results According to the patient's manifestations and imaging findings, besides the COVID-19 pandemic, she was suspected of having COVID-19 and tuberculosis. However, when the aspirated sample was stained, hooklets of E. granulosus were observed. Surgical removal and chemotherapy were used for treatment. Conclusion Treatment of pulmonary cystic echinococcosis is based on surgery, but, along with it, the chemotherapy makes a better prognosis.
Objective(s): Rapid healing of cutaneous leishmaniasis as one of the most important parasitic dis... more Objective(s): Rapid healing of cutaneous leishmaniasis as one of the most important parasitic diseases leads to the decrease of scars and prevention of a great threat to the looks of the affected people. Today, the use of nano-scaffolds is rapidly increasing in tissue engineering and regenerative medicine with structures similar to the target tissue. Chitosan (CS) is a bioactive polymer with antimicrobial and accelerating features of healing wounds, which is commonly used in biomedicine. This study aimed to investigate the effects of CS/polyethylene oxide (PEO)/berberine (BBR) nanofibers on the experimental ulcers of Leishmania major in BALB/c mice. Materials and Methods: CS/PEO/BBR nanofibers were prepared by the electrospinning method, and their morphology was examined by SEM, TEM, and AFM. Then, water absorption, stability, biocompatibility, porosity, and drug release from nano-scaffolds were explored. Afterward, 28 BALB/c mice infected with the parasite were randomly divided int...
With increase of wind power penetrations into the power system, attention to power quality become... more With increase of wind power penetrations into the power system, attention to power quality becomes an important issue. Important aspects of power quality are flicker and harmonics. There are numerous factors that affect on flicker emission and power oscillations of grid-connected wind turbines for example wind characteristics (mean wind speed, tower shadow and wind shear effects and type of used wind turbine) and the grid conditions (short circuit capacity ratio and grid impedance angle) and type of the maximum power point tracking. In the present paper, performances of two maximum power point tracking methods (TSR and OTC) in fluctuations emission are evaluated and fluctuations caused by the tower shadow are then reduced by adding filter when the best MPPT method and grid conditions are selected. All aerodynamic, mechanical and electrical aspects of a wind farm connected to the grid are modeled using FAST and MATLAB/SIMULINK. The simulation results are given and they show well the ...
Objective(s): Various methods for repairing bone defects are presented. Cell therapy is one of th... more Objective(s): Various methods for repairing bone defects are presented. Cell therapy is one of these methods. Bone marrow stromal cells (BMSCs) seem to be suitable for this purpose. On the other hand, lots of biomaterials are used to improve and repair the defect in the body, so in this study we tried to produce a similar structure to the bone by the chitosan and hydroxyapatite. Materials and Methods: In this study, the solution of chitosan-nanohydroxyapatite-polyethylene oxide (PEO) Nanofibers was produced by electrospinning method, and then the BMSCs were cultured on this solution. A piece of chitosan-nanohydroxyapatite Nanofibers with BMSCs was placed in a hole with the diameter of 1 mm at the distal epiphysis of the rat femur. Then the biomechanical and radiographic studies were performed. Results: Biomechanical testing results showed that bone strength was significantly higher in the Nanofiber/BMSCs group in comparison with control group. Also the bone strength in nanofiber/BMS...
International journal of humanities and social sciences, 2016
During the last two decades, many higher education systems in the world has attempted to evaluate... more During the last two decades, many higher education systems in the world has attempted to evaluate and improve the quality of education, research and services at the university and higher education level. Countries which have been successful in these attempts have initiated continuous evaluation and applied internal evaluation as a basis for promoting quality culture. Quality assurance as a comprehensive term encompasses all policies, processes and actions maintaining and developing higher education quality. Quality assurance emphasizes on external goals of evaluation, one of which is to assure learners, public and government that each unit, department, program or institution manages its quality. Thus quality assurance focuses on accountability. In Iran, also, implementation of continuous evaluation projects started in 1996.Then; attempts were made to institutionalize departmental internal evaluation at the university level. This article describes importance of Quality Assurance and ...
Australian journal of basic and applied sciences, 2011
Arsanjan city having green forests and exposure Has great potential to attract tourists Zagross b... more Arsanjan city having green forests and exposure Has great potential to attract tourists Zagross beam is. One of the places in this city forest green Bonab, so in effect each of these factors on willingness to pay and the estimated value of the recreational forest park is Bonab. And for this study were 255 visitors of the study area were selected by simple random sampling, was completed. Visitors of the Logit model to estimate the willingness to pay based on maximum likelihood method was used. The results show that the average willingness to pay for the value of tourist visitors to the park, each visit is 10193.68 Rials. The results also show that variables such as income and educational level of visitors that are statistically significant at one percent, the most important factors affecting the WTP of visitors are from Forest Park Bonab. The next factor to influence the environmental quality of the visitors are WTP, so the statistic is significant at the 5% level. Worth visiting the...
One of the environmental problems in the past two decades has been raising trend of global warmin... more One of the environmental problems in the past two decades has been raising trend of global warming and climate change resulting in destruction and environmental damage. This damage caused by a combination of factors such as population growth, economic growth, international trade and production activities, because these activities increased energy consumption in various economics sectors. The main purpose of this study was to examine the dynamic causal relationship between carbon dioxide diffusion (pollution index), energy consumption, per capita income, foreign trade and GDP of agriculture sector in Iran in 1983-2007. By using a ARDL method and error correction model (ECM), the long run and short-run relationship between variables was evaluated. Results showed a relationship between CO2 diffusion with energy consumption, per capita income and foreign trade. Economic
Objective(s): Design and construction of biocompatible and biodegradable scaffolds are among the ... more Objective(s): Design and construction of biocompatible and biodegradable scaffolds are among the main goals of tissue engineering. Recently, use of nano-hydroxyapatite as a bioactive bioceramic agent with high similarity to the mineral phase of the human bone tissue, in combination with biodegradable polymers and implant coatings has attracted the attention of researchers in the field of biomaterial sciences. The present study aimed to assess the differentiation of bone marrow stromal cells (BMSCs) in osteoblast-like cells on the chitosan/polyethylene oxide (PEO)/nano-hydroxyapatite scaffold in mature rats.Materials and Methods: Chitosan and PEO solution with the weight ratio of 80:20 and 70:30 were prepared, and 2% weight of nano-hydroxyapatite was added. Nanofibers were prepared using the electrospinning method, and the morphology was studied using scanning electron microscopy (SEM). Afterwards, the BMSCs of mature rats were cultured on nanofibers and differentiated by adding a di...
Wind turbine-generators shaft is relatively soft and wind turbine mechanical systems is usually r... more Wind turbine-generators shaft is relatively soft and wind turbine mechanical systems is usually represented as two mass model. Two mass model contains torsional oscillatory modes that may be excited under wind speed variations and grid fault conditions. In this state, torsional oscillations may appear on the output responses of the wind turbine-generator. PMSG based WTs include two converters: machine side converter (MSC) and grid side converter (GSC). The main function of the GSC is the dc-link voltage regulation. Also, the MSC is used to control the generator speed or active power, and thus the control of the generator is mainly carried out by the MSC. There are different strategies for the control of MSC. The purpose of this paper is to study different control strategies of the MSC in the PMSG based WTs. These control strategies include turbine-generator control in speed control mode, power control mode or optimum tip speed ratio mode. Then, performance of the WT by using the men...
Toxoplasma gondii is an intracellular parasite that has been associated with several mental disor... more Toxoplasma gondii is an intracellular parasite that has been associated with several mental disorders. It usually causes an inapparent primary infection. Found worldwide, T. gondii is capable of infecting virtually all warm-blooded animals.1-3Schizophrenia is a neurological disorder characterized with long-term and devastating neuropsychological problems, usually presenting in adolescents or young adults. The disease affects almost 1.1% of the global population including all races and ethnic groups with an equal prevalence in both sexes.1 T. gondii seroprevalence is strongly associated with 12-month generalized anxiety disorder but not with other anxiety, depressive, or alcohol-related disorders. Because of the intracellular nature of some parasites, their treatment and development of new drugs is a major challenge for scientists.4 Recently, the use of nanoparticles and nano-scaffolds has suggested for the treatment of parasitic diseases, although limited research has been done in t...
The system under study in this paper is a real 710 kW DFIG based wind turbine installed in the bi... more The system under study in this paper is a real 710 kW DFIG based wind turbine installed in the binalood site. Based on the measurements and observations of the turbine, at high wind speeds, electromechanical oscillations with frequency of 2 Hz apear on the mechanical system leading to turbine vibration. Control of the wind turbine is carried out based on the power control through a predefined power-speed curve provided by the wind turbine manufacture. The purpose of this paper is to find out the nature and reason of the above mentioned electromechanical oscillations. Hence, the paper first deals with the power control design based on the corresponding power-speed curve. Then, mechanical modes of the system under different operating conditions and wind speeds are extracted. It is shown that at some operating points, low frequency oscillations with frequency of 2 Hz appear on the generator power, generator speed and shaft torsional torque. Next, for improving the damping of the torsional modes, an auxiliary stabilizer control, known as torsional oscillations stabilizer (TOS), is proposed. At the end, simulation results for the system under study are presented.
Background: Leishmaniasis is the most important parasitic disease in Iran and is the third highes... more Background: Leishmaniasis is the most important parasitic disease in Iran and is the third highest rate of rural cutaneous leishmaniasis in the world. Chitosan-polyethylene oxide nanocomposite fibers can be a suitable replacement for ordinary bandages. For the first time, in the absence of any published reports, the present in vitro study aimed to evaluate the anti-leishmanial effects of chitosan (CS)-polyethylene oxide (PEO)-berberine nanofibers on Leishmania major. Methods: The present experimental study was conducted in 2018 in Tehran, Iran. The CS-PEO nanofibers containing berberine, as a natural anti-parasitic agent, were prepared using the electrospinning technique. Biocompatibility and fibroblast proliferation on nanofibers were investigated. In addition, the anti-leishmanial activity of CS-PEO nanofibers in both the promastigote and amastigote stages of Leishmania major was evaluated after parasite vital staining and MTT assay and compared to a control group. Statistical ana...
Hematobium species of this parasite tends to bladder and mesenteric arteries and it causes lesion... more Hematobium species of this parasite tends to bladder and mesenteric arteries and it causes lesions in the bladder wall, urethra, and renal tubes. A 25-year-old man living in Tehran (a non-endemic and very rare area for schistosoma) suffers from symptoms such as hematuria with suprapubic pain, dysuria, fever, nausea and vomiting. Urine analysis showed a lot of red blood cells, after using cystoscopy of the area and receiving a bladder biopsy, a definitive diagnosis of schistosomiasis was made and after determining the extent of damage to the urinary tract, appropriate treatment with surgery and praziquantel (40 mg/kg) were prescribed.
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Papers by Mohsen Rahimi