h.r. heydari

Ratcheting is known as the accumulation of plastic strains resulting from cyclic loadings. In this research، the simulation of a S275 carbon steel sheet's behavior subjected to cyclic thermal loading and axial load has been investigated. This analysis was performed using the finite element method and employing Ansys Parametric Design Language (APDL). This study investigates the Bree diagram and simulates the behaviors specified in this diagram concerning temperature and pressure parameters. According to the results، it turned out that the ratchet strain is always larger in the first cycles than in subsequent cycles. Nevertheless، the plastic strain during cyclic thermal load is equal to the plastic strain while removing the cyclic thermal load in the plastic area. In the shakedown area، after the first plastic strain، elastic behavior occurs in the sheet. Finally، it was found that Bree's diagram has a unique application in predicting the behavior of different types of sheets، and sheets with any dimensions and material can be used to study the behavior of shakedown، ratcheting، elasticity، and plasticity.

To investigate the effects of different nitrogen sources including ammonium nitrate, asparagine, and glutamine in five concentrations of 0, 50, 100,150, and 200 mg l-1 on some physiological and biochemical characteristics of rosemary (Rosmarinus officinalis L.), an experiment was conducted in a completely randomized design with five repliacations. The indices including plant height, shooting rate, number of leaves, necrotic leaf size, chlorophylls a, b, and total chlorophyll content, and the content of carotenoids, phenols, and flavonoids were measured. The results showed that the nitrogen sources significantly (P≤0.01) affected the all measured indices except the necrotic leaf size. The results of means comparison showed that the highest shooting rate and number of leaves were obtained at 100 mg l-1 of glutamine and asparagine and the highest plant height was obtained at 200 mg l-1 of ammonium nitrate. Also, the highest amount of photosynthetic pigments was obtained at 50 mg l-1 of asparagine and the highest amount of phenols and flavonoids was related to 200 mg l-1 of glutamine. In general, the results showed that the various nitrogen sources studied could positively and significantly improve the morphological and physiological characteristics of rosemary under in vitro conditions.