m. alirezaei

The experience of past earthquakes and the weak seismic performance of some structures have highlighted the need for modern seismic systems. Therefore, further examination of lateral seismic systems, such as energy dissipation dampers, is essential for improving the seismic performance of existing systems. Energy dampers can generally be divided into two categories: velocity-based dampers, such as viscous dampers, and displacement-based dampers, such as yielding and friction dampers. Friction dampers are one of the most effective energy dissipating devices in structures, capable of dissipating seismic energy through friction without causing damage (yielding). This paper studies a new system combining a knee-braced frame (KBF) with a friction damper (KBFD). The damper used is a linear friction damper with a slotted bolted connection. The goal of incorporating the friction damper in this configuration is to help prevent out-of-plane buckling of the brace equipped with the damper and to maximize the capacity of damper to improve the seismic performance of the KBF. In this paper, the finite element model of the KBFD was first validated using experimental results. Then, six types of KBFD frames, with varying pre-tension forces in the friction damper considered as a variable parameter, were studied. These studies included performing pushover analysis to calculate the seismic parameters of the structure, such as ductility and behavior factors. The results of these analyses indicate an improvement in the seismic performance of the KBFD compared to the KBF, with both the ductility and behavior factors increasing. Based on the results, with increasing pre-tension force, the behavior factor also increases and is suggested to range between 7.9 and 9.0. Additionally, these frames were subjected to cyclic loading to further study their seismic behavior. The results of the frame analyses were reported as hysteresis curves, initial and secant stiffness, frame resistance, ductility, behavior factor, dissipated energy, and equivalent viscous damping. The results demonstrate that the friction damper effectively reduces the seismic demand on the braces and columns. Furthermore, the obtained hysteresis curves show a high level of input earthquake energy dissipation and appropriate seismic performance of the frames with the proposed configuration.

Angoumois grain moth, Sitotroga cerealella, is one of the most critical storage pests with a wide range from the hosts in Iran and worldwide. Excessive consumption of chemical insecticides leads to developing the resistance to chemical insecticides, environmental pollution, and the emergence of new pests. Therefore, we have decided to reduce the risk of the environment in pest’s control via plant essential oils.

In the current study, to examine the environment- friendly pesticides, effects of three plant essential oils from the families Mentha longifolia L., Thymus daenensis Celak (Lamiaceae), and Artemisia aucheri Boiss (Asteraceae) compared to dichlorvos (DDVP®,as a positive control) an organophosphate insecticide were studied. Antioxidant enzymes, including: superoxide dismutase (SOD), catalase (CAT), and lipid peroxidation marker on the fourth instar larvae of S. cerealella after 24 hours were examined. The essential oils were prepared using the water distillation method. Essential oils were used in five concentrations and three replications. The concentration was selected based on the primary experiment for each essential oil. Insects were exposed to fumigant toxicity of the essential oils and insecticide in laboratory conditions (25±1 °C, 70±5% in 12 hr light/12 hr dark).

The results showed that LC50 for the essential oils of M. longifolia, T. daenensis, and A. aucheri were recorded 0.04, 0.68 and 6.47 μL/Lair, respectively. The highest mortality rate increased with high concentrations (0.09, 3 and 9 μL/Lair) of M. longifolia, T. daenensis and A. aucheri essential oil were 84, 80.67, and 77.33 %, respectively after 24h. Enzymatic activity increased with essential oil high concentrations. Data indicated a significant increase in the activity of catalase, superoxide dismutase enzymes and the concentration of malondialdehyde as peroxidation lipid indicator in treated larvae with essential oils of M. longifolia, T. daenensis and A. aucheri compared with the untreated (negative control), and DDVP® (positive control) on treated 4th instar larvae of S. cerealella after 24h. 

 Conclusion

It seems that different essential oils of M. longifolia, T. daenensis and A. aucheri with the effect on the enzymatic activities of antioxidants, including catalase, superoxide dismutase enzymes and malondialdehyde as lipid peroxidation indicator of the fourth instar larvae of S. cerealella via the disruption of physiological processes and survival. Regarding the existence of different aromatic plants in Iran, we can use the species with higher toxicity that would be more economical to produce the botanical insecticides and use in the integrated pest management programs for this pest control.