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Papers by Mohsen Afsahi Zadeh
Rising energy demand and at the same time global effort to reduce greenhouse gases are strong pus... more Rising energy demand and at the same time global effort to reduce greenhouse gases are strong pushes for harvesting renewable energy sources in remote areas far away from consumption centers. Ultra High Voltage Direct Current is a highly efficient way to transfer bulk power over long distances. One key component for the reliable energy transfer in this technology is HVDC converter transformer. The insulation system of HVDC converter transformers, which basically consists of oil and paper/pressboard with different dielectric properties, needs to withstand AC and DC stresses. In particular for the UHVDC application the transient phenomenon of electric stress due to space charges needs to be further understood in order to design an insulation system for safe operation during long service life time. A physical model commonly called the ion drift model describes space charge accumulation on solid-liquid interface by ion transport in liquid. One important parameter in this model is the ion mobility. An investigation was made to evaluate the experimental set up for ion mobility measurement in COMSOL Multiphysics®. Charge transport, electric field distributions and current curves were studied in a bulk of oil under dc voltage application. After analyzing the simulation result decision concerning the setup type was made by having two factors in mind: accuracy and large enough signal to determine the mobility. Based on the physical picture of the ion movement in the transformer oil obtained by the numerical calculation, the plane parallel electrode geometry had been chosen for experiment. The evolution of instrument and software for data acquisition during the experiment enabled us to get the desired data. The measurements were carried out for two types of dielectric liquid: mineral oil and natural ester oil. By obtaining information on the time of flight from the current curves, the mobility of ions in positive and negative voltage application for the respective liquids were determined. For mineral oil the measured mobility was around 2.
Arak Medical University Journal, Oct 15, 2013
2012 International Conference on High Voltage Engineering and Application, 2012
ABSTRACT Conduction process in dielectric liquids usually occurs due to ion migration and is ther... more ABSTRACT Conduction process in dielectric liquids usually occurs due to ion migration and is therefore characterized by concentration and mobility of the ionic charge carriers. For this reason accurately determining these parameters and especially ion mobility in insulating oils for HVDC applications needs to be done precisely. In this report various methods for determining ion mobility are described, including single polarity, reversal polarity methods in time domain as well as frequency domain based measurement of dielectric response. The advantages and disadvantages of each of them are presented and illustrated with the results of measurements on various oils using two different test cells. The dependence of ion mobility on measuring voltage level and temperature are analyzed and compared.
Journal of Oral and Maxillofacial Surgery, 2005
1. J Oral Maxillofac Surg. 2005 Jul;63(7):1035-9. Melkersson-Rosenthal syndrome: case report of a... more 1. J Oral Maxillofac Surg. 2005 Jul;63(7):1035-9. Melkersson-Rosenthal syndrome: case report of a 30-year misdiagnosis. Gerressen M, Ghassemi A, Stockbrink G, Riediger D, Zadeh MD. Department of Oral and Maxillofacial ...
Journal of Oral and Maxillofacial Surgery, 2006
The goal of this retrospective study was to examine whether utilization of condylar positioning d... more The goal of this retrospective study was to examine whether utilization of condylar positioning devices in bilateral sagittal split osteotomy leads to long-term benefits for temporomandibular joint function as compared with the manual positioning technique. Patients and Methods: The joint function of 49 patients (98 joints) who underwent bilateral sagittal split osteotomy or bimaxillary osteotomy at the University Hospital of Aachen between 1993 and 2003 was analyzed by recording joint movements with axiography supported by clinical examination of the temporomandibular joint. In 10 patients out of 28 with mandibular advancement and in 10 out of 21 with mandibular setback the Luhr positioning device was used intraoperatively to reproduce the condylar position. The joints of the remaining patients were positioned manually. The received data were statistically evaluated by using unrelated t test at P ϭ .05. Results: In mandibular advancement the manually positioned group showed significantly less signs of temporomandibular disorders, while there were slight advantages in axiographically measured joint track lengths for the patients who were operated with positioning devices. After mandibular setback surgery clinical analysis as well as axiography presented comparable results in both groups. Conclusion: The use of a positioning device did not provide a better functional outcome long term in either mandibular advancement or setback surgery. With the manual positioning technique, an at least equally good temporomandibular joint function was attained.
International Journal of Antimicrobial Agents, 2014
Oral health & preventive dentistry, Jan 27, 2014
Purpose: To compare the efficacy of an Aloe vera mouthwash with a benzydamine mouthwash in the al... more Purpose: To compare the efficacy of an Aloe vera mouthwash with a benzydamine mouthwash in the alleviation of radiation- induced mucositis in head and neck cancer patients using a triple-blind, randomised controlled trial. Materials and Methods: Twenty-six eligible head and neck cancer patients who were to receive conventional radiation therapy at the radiation oncology department were randomised to receive an Aloe vera mouthwash or a benzydamine mouthwash. Mucositis severity was assessed during the course of radiation therapy using the WHO grading system. Results: At baseline, there was no difference in the distribution of mucositis severity between the two groups. The mean interval between radiation therapy and onset of mucositis was similar for both groups (Aloe vera 15.69 ± 7.77 days, benzydamine 15.85 ± 12.96 days). The mean interval between the start of radiation therapy and the maximum severity of mucositis were was also similar in both the Aloe vera and benzydamine groups (A...
In the present study, Al based nano-composites with 1.00 wt.% of nano-sized Al 2 O 3 particulates... more In the present study, Al based nano-composites with 1.00 wt.% of nano-sized Al 2 O 3 particulates reinforcement were produced and its mechanical properties was investigated. A mechanical method utilized in order to refine the second phase particles. The synthesis of nanocrystalline Al 2 O 3 is almost complete after 20 hours milling and particles with average size of 46 nm obtained. Subsequently, 1.00 wt.% Al 2 O 3 was added to molten Al. Characterising of the mechanical activated powder, using scanning electron microscopy (SEM) and X_ray diffraction (XRD), verified well distribution of the particle size. Furthermore, different mechanical properties of the composite and pure alominum was compared. Addition of a small amount of Al 2 O 3 to the Al matrix improves the hardness, wear resistance and compression strength significantly. The results proved that the method used in this study could improve the mechanical properties of alumium.
ABSTRACT Landfill siting should take into account a wide range of territorial and legal factors i... more ABSTRACT Landfill siting should take into account a wide range of territorial and legal factors in order to reduce negative impacts on the environment. This research focused on determining suitable locations for construction of a suitable disposal centers. So in first stage, effective factors in site selection of waste landfill in Amol in Mazandaran county, Iran were considered; another stage consists of making numerical and weighting the 8 layers according to existent standards which include: slope, erosion, distance to fault, distance to surface waters, depth to ground waters, distance to agricultural lands and gardens, distance to road, distance to power transition lines, and entering mentioned layers into IDRISI and Arc GIS software and establishing specific databases for urban waste landfill and implementing different models of analytic multi criteria decision making such as analytic hierarchy process and weighted linear combination on current layers. Results of this research indicated that weighted linear combination in primitive stage have higher decision making power in locating burying place than analytic hierarchy process through choosing three site and at the end by selecting final site for waste landfill in south of Amol. At the end, through overlapping and also compounding similarities of these models in Arc GIS software, a site with 110 hectare area and accepting 170 ton waste per day for 20 years, was selected as recommended and final place of waste landfill in Amol. Results shows that this instrument has the potential to assist planners, decision makers and other agents involved in the process of selecting suitable sites for municipal landfills.
Rising energy demand and at the same time global effort to reduce greenhouse gases are strong pus... more Rising energy demand and at the same time global effort to reduce greenhouse gases are strong pushes for harvesting renewable energy sources in remote areas far away from consumption centers. Ultra High Voltage Direct Current is a highly efficient way to transfer bulk power over long distances. One key component for the reliable energy transfer in this technology is HVDC converter transformer. The insulation system of HVDC converter transformers, which basically consists of oil and paper/pressboard with different dielectric properties, needs to withstand AC and DC stresses. In particular for the UHVDC application the transient phenomenon of electric stress due to space charges needs to be further understood in order to design an insulation system for safe operation during long service life time. A physical model commonly called the ion drift model describes space charge accumulation on solid-liquid interface by ion transport in liquid. One important parameter in this model is the ion mobility. An investigation was made to evaluate the experimental set up for ion mobility measurement in COMSOL Multiphysics®. Charge transport, electric field distributions and current curves were studied in a bulk of oil under dc voltage application. After analyzing the simulation result decision concerning the setup type was made by having two factors in mind: accuracy and large enough signal to determine the mobility. Based on the physical picture of the ion movement in the transformer oil obtained by the numerical calculation, the plane parallel electrode geometry had been chosen for experiment. The evolution of instrument and software for data acquisition during the experiment enabled us to get the desired data. The measurements were carried out for two types of dielectric liquid: mineral oil and natural ester oil. By obtaining information on the time of flight from the current curves, the mobility of ions in positive and negative voltage application for the respective liquids were determined. For mineral oil the measured mobility was around 2.
Arak Medical University Journal, Oct 15, 2013
2012 International Conference on High Voltage Engineering and Application, 2012
ABSTRACT Conduction process in dielectric liquids usually occurs due to ion migration and is ther... more ABSTRACT Conduction process in dielectric liquids usually occurs due to ion migration and is therefore characterized by concentration and mobility of the ionic charge carriers. For this reason accurately determining these parameters and especially ion mobility in insulating oils for HVDC applications needs to be done precisely. In this report various methods for determining ion mobility are described, including single polarity, reversal polarity methods in time domain as well as frequency domain based measurement of dielectric response. The advantages and disadvantages of each of them are presented and illustrated with the results of measurements on various oils using two different test cells. The dependence of ion mobility on measuring voltage level and temperature are analyzed and compared.
Journal of Oral and Maxillofacial Surgery, 2005
1. J Oral Maxillofac Surg. 2005 Jul;63(7):1035-9. Melkersson-Rosenthal syndrome: case report of a... more 1. J Oral Maxillofac Surg. 2005 Jul;63(7):1035-9. Melkersson-Rosenthal syndrome: case report of a 30-year misdiagnosis. Gerressen M, Ghassemi A, Stockbrink G, Riediger D, Zadeh MD. Department of Oral and Maxillofacial ...
Journal of Oral and Maxillofacial Surgery, 2006
The goal of this retrospective study was to examine whether utilization of condylar positioning d... more The goal of this retrospective study was to examine whether utilization of condylar positioning devices in bilateral sagittal split osteotomy leads to long-term benefits for temporomandibular joint function as compared with the manual positioning technique. Patients and Methods: The joint function of 49 patients (98 joints) who underwent bilateral sagittal split osteotomy or bimaxillary osteotomy at the University Hospital of Aachen between 1993 and 2003 was analyzed by recording joint movements with axiography supported by clinical examination of the temporomandibular joint. In 10 patients out of 28 with mandibular advancement and in 10 out of 21 with mandibular setback the Luhr positioning device was used intraoperatively to reproduce the condylar position. The joints of the remaining patients were positioned manually. The received data were statistically evaluated by using unrelated t test at P ϭ .05. Results: In mandibular advancement the manually positioned group showed significantly less signs of temporomandibular disorders, while there were slight advantages in axiographically measured joint track lengths for the patients who were operated with positioning devices. After mandibular setback surgery clinical analysis as well as axiography presented comparable results in both groups. Conclusion: The use of a positioning device did not provide a better functional outcome long term in either mandibular advancement or setback surgery. With the manual positioning technique, an at least equally good temporomandibular joint function was attained.
International Journal of Antimicrobial Agents, 2014
Oral health & preventive dentistry, Jan 27, 2014
Purpose: To compare the efficacy of an Aloe vera mouthwash with a benzydamine mouthwash in the al... more Purpose: To compare the efficacy of an Aloe vera mouthwash with a benzydamine mouthwash in the alleviation of radiation- induced mucositis in head and neck cancer patients using a triple-blind, randomised controlled trial. Materials and Methods: Twenty-six eligible head and neck cancer patients who were to receive conventional radiation therapy at the radiation oncology department were randomised to receive an Aloe vera mouthwash or a benzydamine mouthwash. Mucositis severity was assessed during the course of radiation therapy using the WHO grading system. Results: At baseline, there was no difference in the distribution of mucositis severity between the two groups. The mean interval between radiation therapy and onset of mucositis was similar for both groups (Aloe vera 15.69 ± 7.77 days, benzydamine 15.85 ± 12.96 days). The mean interval between the start of radiation therapy and the maximum severity of mucositis were was also similar in both the Aloe vera and benzydamine groups (A...
In the present study, Al based nano-composites with 1.00 wt.% of nano-sized Al 2 O 3 particulates... more In the present study, Al based nano-composites with 1.00 wt.% of nano-sized Al 2 O 3 particulates reinforcement were produced and its mechanical properties was investigated. A mechanical method utilized in order to refine the second phase particles. The synthesis of nanocrystalline Al 2 O 3 is almost complete after 20 hours milling and particles with average size of 46 nm obtained. Subsequently, 1.00 wt.% Al 2 O 3 was added to molten Al. Characterising of the mechanical activated powder, using scanning electron microscopy (SEM) and X_ray diffraction (XRD), verified well distribution of the particle size. Furthermore, different mechanical properties of the composite and pure alominum was compared. Addition of a small amount of Al 2 O 3 to the Al matrix improves the hardness, wear resistance and compression strength significantly. The results proved that the method used in this study could improve the mechanical properties of alumium.
ABSTRACT Landfill siting should take into account a wide range of territorial and legal factors i... more ABSTRACT Landfill siting should take into account a wide range of territorial and legal factors in order to reduce negative impacts on the environment. This research focused on determining suitable locations for construction of a suitable disposal centers. So in first stage, effective factors in site selection of waste landfill in Amol in Mazandaran county, Iran were considered; another stage consists of making numerical and weighting the 8 layers according to existent standards which include: slope, erosion, distance to fault, distance to surface waters, depth to ground waters, distance to agricultural lands and gardens, distance to road, distance to power transition lines, and entering mentioned layers into IDRISI and Arc GIS software and establishing specific databases for urban waste landfill and implementing different models of analytic multi criteria decision making such as analytic hierarchy process and weighted linear combination on current layers. Results of this research indicated that weighted linear combination in primitive stage have higher decision making power in locating burying place than analytic hierarchy process through choosing three site and at the end by selecting final site for waste landfill in south of Amol. At the end, through overlapping and also compounding similarities of these models in Arc GIS software, a site with 110 hectare area and accepting 170 ton waste per day for 20 years, was selected as recommended and final place of waste landfill in Amol. Results shows that this instrument has the potential to assist planners, decision makers and other agents involved in the process of selecting suitable sites for municipal landfills.