@article { author = {Mehrabian, A.L. and Dr. Roshanian, Jafar}, title = {Near - Optimal Tunning of Linear Controllers Based on Genetic Algorithm and Swarm Intelligence: A Flight Control Example}, journal = {Journal of Aerospace Science and Technology}, volume = {4}, number = {2}, pages = {1-12}, year = {2007}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {}, keywords = {}, url = {https://jast.ias.ir/article_51534.html}, eprint = {https://jast.ias.ir/article_51534_687e557a35f629a5abe2e0fb1ff890af.pdf} } @article { author = {Farshchi, Mohammad}, title = {Three Dimensional Stability Analysis of a Liquid Propellant Combustor}, journal = {Journal of Aerospace Science and Technology}, volume = {4}, number = {2}, pages = {13-22}, year = {2007}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {A theoretical study analyzing three-dimensional combustion acoustic instabilities in a liquid propellant rocket engine combustor has been conducted. A linear theory based on Crocco’s pressure sensitive time lag model is used. To apply this theory the combustor is divided into two main components, including the combustion chamber and the converging part of the nozzle. The assumption of concentrated combustion zone is used and the governing perturbation equations describing oscillations of flow variables are considered. To solve these equations appropriate boundary conditions at both ends of the combustion chamber are required. Combustion zone boundary condition at one end and the nozzle admittance relation at other end are used. To obtain the nozzle admittance the three dimensional flow perturbation equations are solved in the converging part of the nozzle. This approach is capable of predicting acoustic stability behavior of a combustor at a wide range of Mach numbers and frequencies. Also, this analysis enables the rocket engine designer to observe the effects of different parameters such as nozzle entrance Mach number, chamber geometry, nozzle geometry, and gas properties on stability characteristics of an engine combustor. In case of instability observation; one can predict the acoustic mode which causes the instability and achieve an optimum design before conducting any expensive and time consuming experimental tests. This paper presents the stability analysis results and a parametric study of the effect of design parameters on stability characteristics of a typical combustor.}, keywords = {}, url = {https://jast.ias.ir/article_51535.html}, eprint = {https://jast.ias.ir/article_51535_c5e9384afc246a91dbb2ec02eb2d7be5.pdf} } @article { author = {Javanmard, Soheila and Bodagh jamali, J.}, title = {A Numerical Model to Investigate Optimum Liquid Carbon Dioxide Seeding Rate in Weather Modification Projects}, journal = {Journal of Aerospace Science and Technology}, volume = {4}, number = {2}, pages = {23-31}, year = {2007}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {}, keywords = {}, url = {https://jast.ias.ir/article_51536.html}, eprint = {https://jast.ias.ir/article_51536_c373729594a0ee07e46735e756891aed.pdf} } @article { author = {}, title = {Sensitivity Analysis of Different Convection Schemes and Center Domains for Numerical Simulation of Winter Precipitation Over Iran}, journal = {Journal of Aerospace Science and Technology}, volume = {4}, number = {2}, pages = {33-42}, year = {2007}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {This paper qualifies the effect of different convection schemes and center-domains on the simulation of winter precipitation over Iran using RegCM3 numerical climate model. It is compressible, finite difference with hydrostatic equilibrium in sigma coordinate with a semi-implicit algorithm for reduction of horizontal diffusion. Iran experienced two dry and wet periods during winters of 1997 and 2000. In this paper sensitivity of the RegCM3 regional climate model has been analyzed using different convection schemes, including Grell-AS, Grell- FC, Emanuel and Kuo and different center domains including Himalaya, Mediterranean sea, Iran and Indian ocean (near Pakistan southern boundaries). NNRP1 data with 5 degree resolution, GLCC and GTOPO are used as initial and boundary conditions, land use and topography data, respectively. We found that there is an intelligence between model skill and center domain, for example Himalaya center domain gives good results when a Siberian high pressure develops over Iran. The minimum bias and MAE of -0.7mm and 0.6mm are captured by Kuo convection scheme in the modeling of dry year 2000, but Grell convection scheme have minimum error among two wet and dry winter simulation. Precipitation amounts are underestimated for both convection and center domain experiments when compared to observations during winter 2000. The largest difference occurred in Himalaya experiment. We found that CRU reanalysis data can not be considered as a reference data for calibration of RegCM3 over Iran. It is also found that there is an eastward shift in Caspian Sea precipitation pattern in all experiments.}, keywords = {RegCM3,Climate model,winter precipitation,Sensitivity analysis,Iran}, url = {https://jast.ias.ir/article_51537.html}, eprint = {https://jast.ias.ir/article_51537_52853d46510670a151ce7db6cdd98075.pdf} } @article { author = {Nategh, M.J.}, title = {Analytical and Experimental Investigations on Influential Parameters of Superplastic Forming of Titanium Based Workpieces}, journal = {Journal of Aerospace Science and Technology}, volume = {4}, number = {2}, pages = {43-51}, year = {2007}, publisher = {Iranian Aerospace Society}, issn = {1735-2134}, eissn = {2345-3648}, doi = {}, abstract = {}, keywords = {}, url = {https://jast.ias.ir/article_51538.html}, eprint = {https://jast.ias.ir/article_51538_e96168006d0632a864b72c0dad22964a.pdf} }