فهرست مطالب b. shahriari

Structure optimization in aerospace industries is of particular importance due to the need for light structures to reduce costs and increase flight performance. The main components of an airplane wing consist of spars, ribs and skin. At first, in this research a wing structure with two I-shaped spars, 6 ribs and a shell with specific geometric characteristics is modeled. By choosing aluminum alloy as the material of the structure and using the finite element method, the wing structure has been subjected to static loading and the maximum amount of stress and displacement of the wing box area has been obtained. Then, according to the results of the analysis and the optimization capability, the wing structure has been divided into three parts in order to optimize the thickness of the components along the length of the wing. By defining the thickness of the wing box components in all three parts as factors and stress and weight as the answers to the optimization problem through the method of designing experiments, which in this problem is the static analysis of the structure, the thickness of the components of the wing box area according to the goal of the lowest weight and the highest stress Optimization is allowed. The obtained results indicate that after the optimization, the weight of the wing box has decreased by 46.5%.

Aerospace engines testing is a source of noise pollution and determining the low frequency acoustic characteristics of the test cell, plays an important role in optimally control of the sound field and reducing the level of sound pressure and pollution. In this study, the drop in average sound pressure level is numerically predicted by constructing a test cell according to ISO 140 standard. To solve the sound propagation equations, modeling the contact between the structure and the fluid, dynamic coupling of the structure and the fluid is performed and to calculate the acoustic energy distribution in the fluid and the structure, Abaqus finite element software is used. Cells with different dimensions and insulation and simply support conditions are modeled and the average sound pressure level drop of each model is calculated and compared. The optimal dimensions of the cell are determined, then the independence of the mesh is checked and the results are verified using experimental data. The measured sound pressure drop values are reported for the quarter band. To ensure that it is not resonated by acoustic force, the frequency analysis of the structure was performed and it was determined that the designed test cell eliminates noise pollution. Cell size optimization shows that the best test cell radius for the 90 to 150 Hz frequency range is 2.25 m.

One of the cultivars of table grape in Iran is Vitis vinifera cv. Askari. But the smallness and non-uniformity of berry size have reduced its yield and attractiveness for consumers. Application of gibberellic acid, nutrients such as potassium as well as 2,4-D at the correct time can enhance the plant growth and fruit development. This study aimed to determine the most suitable gibberellic acid, 2,4-D, and potassium resources on quantitative and qualitative characteristics of Askari grape. This study was conducted on a research farm, on 30-year-old grapevine vines in the Koshkak region of Fars province of Iran in 2016. This experiment was arranged in a randomized complete block design with nine treatments and four replicates. Gibberellic acid at 50 mg/L, 2,4-D at 5, 10 and 20 mg/L, 10 mg/L 2,4-D + 50 mg/L GA3, 50 mg/L GA3 + 10 mg/L 2,4-D + 15 g/L K2SO4, 50 mg/L GA3 + 10 mg/L 2,4-D + 15 g/L KNO3, 50 mg/L GA3 + 10 mg/L 2,4-D + 15 g/L KCl and Distilled water as a control were used. The highest berry and cluster weights and lowest soluble solids content and total phenol were obtained in the treatment of 50 mg/L GA3+10 mg/L 2,4-D+15 g/L K2SO4 with mean of 2.58 g, 214 g and 14.25 ᵒBrix and 58.77 mg/kg, respectively. The lowest berry and cluster weights (1.70-118 g) were obtained from the 20 mg/L 2,4-D treatment. Also, the highest soluble solids content and anthocyanin were obtained from treatment of 20 mg/L 2,4-D with an average of 18.5 ᵒBrix and 41.71 mg/kg, respectively. Results have shown that the use of 50 mg/L of GA3 with 10 mg/L 2,4-D and the use of potassium sources, especially K2SO4 increased the yield and uniformity of the cluster and berry size.