فهرست مطالب hosein shabani

Evaluation of the type and concentration of microorganisms in the air of a hospital can be an indicator of whether such environments are clean or not, and also to be considered as a source of nosocomial infections. The aim of this study was to identify the type and concentration of Bio-aerosols associated with nosocomial infections in different wards of selected AJA hospitals in Tehran.
In a cross-sectional and descriptive- analytical study 120 bacterial and 120 fungal samples were collected from the operation rooms, Intensive Care Units (ICUs) and Infectious diseases wards of two studied hospitals (A and B). A passive indoor environment sampling was carried out within 120 days, once every six days.
The average concentration of bacteria in the air of A and B hospitals were 84 and 212 CFU/m3, respectively. Also, the Average concentration of fungal species of A and B hospitals were was 80 and 85 CFU/m3, respectively. The dominant fungal species of these hospitals were Cladosporium (25%) and Aspergillus niger (28%), respectively. Also, Staphylococcus epidermidis was determined as the dominant bacterial species in both hospitals. Significant linear correlation existed between population density and concentration of bio-aerosols.
According to the results of this study, bacterial and fungal bio-aerosol concentrations in the studied hospitals were higher than the existing standards and it indicates the low efficiency of the ventilation system in these hospitals.

In this paper optimal design and effectiveness assessment of active multiple tuned mass dampers (AMTMDs) in reducing the vibration of nonlinear hysteretic structures has been studied. For active control of nonlinear structures the Newmark-based instantaneous optimal control algorithm has been used. Optimal parameters of AMTMDs and weighting matrices of active control performance index have been determined based on minimization of the maximum required control force of ATMDs to below the maximum drift of structure to a specified limit. For solving the optimization problem which includes a large number of variables, genetic algorithm (GA) has been applied. For numerical simulation, an eight–storey shear frame with bilinear hysteretic behavior subjected to white noise excitation and for different values of MTMDs mass ratio and ATMDs number, optimal AMTMDs have been designed. Also the efficiency of the AMTMDs mechanism under both near-fault and far-fault earthquakes has been tested. The results of numerical simulations show the effectiveness of the proposed method in designing AMTMDs on nonlinear structures. Also, it has been concluded that using AMTMDs could be effective in mitigating the damage of nonlinear structures which the amount of reduction depends on the input earthquake characteristics, AMTMDs mass ratio and ATMDs number.

In this research، the effectiveness of multiple tuned mass dampers (MTMDs) in mitigating the response of nonlinear hysteretic structures has been studied where the optimal parameters of MTMDs have been determined based on minimization of maximum relative displacement (drift) of structure. For solving the optimization problem the genetic algorithm (GA) has been used successfully. For numerical analysis، an eight-storey bilinear hysteretic shear frame subjected to a white noise excitation and optimal MTMDs have been designed. The results of numerical simulations have shown the effectiveness of the proposed method in designing optimal MTMDs for nonlinear structures. Also، it can be said that the damage of structure can be reduced using optimal MTMDs where the performance has been affected by earthquake characteristics and mass ratio.