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Showing 5 results for سمائی


Volume 13, Issue 13 (First Special Issue 2014)
Abstract

High temperatures and different properties of entering gas into the turbine of a gas turbine cycle can decrease its performance. Considering the complexity of the flow distribution inside the turbine, three-dimensional analysis to find out the flow and temperature field in the turbine stages is very important. As time passing the increasing of the roughness of blades is unavoidable. The aim of this paper is investigation of the blades roughness effects on flow field and efficiency of gas turbine with numerical calculations. In this research, a two-stage turbine is modeled in the form of three-dimensional and the results are validated with experimental data. Then the effects of blades roughness on flow field and performance of turbine in five pressure ratios is investigated. Also, in order to determine the role of stators and rotors in decreasing the turbine efficiency, in a special roughness, the first and second stators and then corresponding rotors have separately been examined and then this phenomenon affected on blades simultaneously. Results showed that the efficiency drop by applying all together on the turbine stage is approximately equal to summation of efficiency drops by applying separately.

Volume 14, Issue 4 (3-2012)
Abstract

Objective: The use of antiretroviral drugs has proven remarkably effective in controlling the progression of human immunodeficiency virus (HIV) disease, but these benefits can be compromised by the development of drug resistance. This study aims to assess the drug resistance profile of the Pr gene in highly active antiretroviral therapy (HAART)-treated and naïve HIV-1 infected patients. Methods: A total of 30 samples from naïve and 16 samples of highly active antiretroviral therapy (HAART)-treated patients were collected and divided into two groups. After RNA extraction, RT nested PCR was performed. The final products were sequenced and then analyzed for drug-resistant mutations and subtypes. Results: No drug resistant mutations were noted in group one that have never used drug, but 40% of group two samples which are under treatment contained drug resistant mutations. According to the results, the following subtypes were seen among patients: A (50%), B (40.6%), D (6.2%), and C (3.2%). Conclusion: Transmission of drug-resistant viruses and their detection are very important epidemiologically. However our data and other studies suggest that other PIs should be replaced by LPV in the HAART regime.

Volume 14, Issue 15 (Third Special Issue 2015)
Abstract

With respect to special conditions apply to the gas turbine, its blades are affected by many different factors such as, hot corrosion, oxidation, wear, impact of external particles, and etc. and are destroyed. Due to the reduction of their working life time, the turbine efficiency reduces and ultimately the heavy costs of periodic repairs are needed, and also new replacements of their blades are unavoidable. The aim of this study is investigation of the effects of corrosion and blade damage on flow field and gas turbine performance, by numerical simulation. In this research, a two stage turbine is modeled in the form of three dimensional and the results are validated with experimental data. To analyze of the behavior of entire flow, conservation of mass, momentum, and energy equations are solved. The numerical simulation of the turbine is done with ANSYS CFX software. Then the increased rotors tip clearance effects with decreasing thickness due to corrosion in both nozzles and blade leading edge and trailing edge were separately studied on turbine flow field and its performance in five actual different pressure ratios. The results showed that the most important factor in reducing the efficiency of gas turbine is due to rotor tip clearance increasing. Also corrosion of the blade edge respect to the trailing edge damage is a little more affected on reducing efficiency and increasing loss coefficients.

Volume 14, Issue 65 (0-0)
Abstract



Volume 15, Issue 11 (1-2016)
Abstract

Transporting an object using several mobile robots by formation control, is an effective method in handling heavy and complicated objects either in known and unknown places. In this paper, to control the formation of three mobile robots and also to control interactive a control algorithm has been designed based on semi-active suspension system of remote center compliance (RCC). The main objective of control structure of semi-active suspension system is to control the desired formation and appropriate transportation of the object at the same time and also separating the object and other robots from effect of the errors occurred while creation of disturbance in a certain robot and preventing it from having effects on other robots. In order to terminate instability in impedance methods, multiple impedance control has been used in moving the object by cooperating robots. To follow the desired path and control of mobile robots formation, Leader follower method has been used. Simulation results indicate that the semi-active suspension control system, in order to minimize the vibrations caused by disturbance transferred to the set of robots, is more optimum and more stable compared to passive suspension control system.

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