Showing 4 results for Asilian
A. Khavanin, K. Azrah, R. Mirzaei, S. B. Mortazavi, H. Asilian, A. Soleimanian,
Volume 4, Issue 2 (7-2014)
Abstract
Introduction: Whole body vibration occurs when human is on a vibrating surface and the vibration influences parts of the body which are far from the contacted part. Up to now, various health-related problems due to whole body vibration have been reported, including back pain, sciatica, gastrointestinal problems, genital problems and hearing impairment. In the present research, vibration was measured about 2000 minutes in 23 train of 4 active lines of Tehran metro in order to determine the rate of subway drivers’ exposed to whole body vibration.
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Material and Method: Vibration meter and SVAN 958 analyzer, made by Svantek company, were utilized for measuring the whole body vibration. The level of weighted r.m.s acceleration for each axis, the combination of axes, peak factor, VDV and other common exiting ratios in the standard were measured and calculated according to ISO 2631-1.
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Result: Findings showed that according to Basic method drivers exposure to vibration is less than the lowest value of health guide critical region (<0.45m/s2). However, based on Vibration Dose Valuation (VDV), the exposure of 12 cases were higher than the lowest value (<8.5 m/s1.75) and only 11 cases were lower than the mentioned amount.
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Conclusion: Investigation of the result obtained from Basic method and VDV method manifested different amounts of vibration exposure in a way that VDV predicts higher level of risk, compared to basic method. The results shows that some presented indicators can not presented the safe zone in human vibration evaluations.
Hassan Rajabi-Vardanjani, Hassan Asilian-Mahabadi, Morteza Bayareh, Morteza Sedehi,
Volume 9, Issue 4 (12-2019)
Abstract
Introduction: Usually, in the toxicological studies of airborne particulate pollutants, inhalation exposure chambers are used for providing and distributing the test atmosphere uniformly and stability in the respiratory zone of laboratory animals. The purpose of this study was to design, evaluate and optimize a whole-body exposure chamber, specifically for small laboratory animals exposed to particulate matter.
Material and Methods: In the first, the papers and scientific resources which had provided the technical details and performance of the inhalation exposure chambers were studied, and the advantages, disadvantages and those factors affecting their performance were extracted. Then the assumptions of the initial design of the chamber were prepared with regard to the principles of fluid dynamics and the standard conditions of lab animal housing. To create a uniform distribution of particles inside the chamber, guide plates of flow were used in the upper cone. Numerical simulation and ANSYS Fluent software were used to optimize the initial design. Drawing geometry of the chambers was done using Design modeler software and meshing of the computational field using ANSYS meshing software. The particles used had a mean aerodynamic diameter of 10 μm, spherical, inert, and a density of 1,400 kg. m^-3 and entered the chamber at the carrier gas velocity. Particle concentration was measured in the chambers along the cylindrical radius at 10 cm intervals on the x-axis. Then the percentage of variation coefficient of the particle concentration for each line was calculated. In the final analysis of the results, the geometry design with the lowest coefficient of variation of particle concentration along the selected sampling line was selected as the best chamber design.
Results: The optimized inhalation chamber has a dynamical flow and consists of a cylinder with two upper and lower cones. The flow enters from the upper cone and after passes through the guide plates, distributes in the interior of the chamber and exits from the lower cone. The k-ε turbulence and Discrete Phase Models could have modeled this problem. Design No. 7 was optimal design with the lowest coefficient of variation of the concentration (4.08%).
Conclusion: The numerical simulation method for planning and optimizing of the chambers, at a much lower cost than the empirical methods, was able to provide comprehensive information on the solution field. The analysis of this information led to the selection of the best chamber design to provide uniform concentration of the particles in the respiratory region of the animals.
Razieh Janizadeh, Ali Kavanin, Mohammad Sharif Hosseini, Elham Yahyaei, Atefeh Mohammadi Nejad, Hasan Asilian Mahabadi,
Volume 11, Issue 2 (6-2021)
Abstract
Introduction: Regarding the daily growth of Volatile Organic Compounds (VOCs) application in a vast variety of industries which also contributed to their adverse effects, different methods were used for controlling their emission. One of the most effective methods for this purpose, is a combination of cold plasma and catalyst or photo catalyst. In this study, the effectiveness of the HZSM-5/ Tio2 for Toluene treatment removal was investigated
Material and Methods: HZSM-5 zeolite, and Tio2 in 3 and 8 weight percent were used for photo catalyst preparation. The TiO2 particles were coated on the zeolite by impregnation method. X-Ray Diffraction, Scanning Electron Microscope and Brunauer Emmett Teller tests were used for the identification of photo catalyst structural properties. Toluene vapors with 58±2 PPM concentrations were produced in ambient condition including the room pressure and temperature by a dynamic system and introduced to a reactor included 1 gr of the photo catalyst. Vapors were passed from the reactor continuously with a rate of 0.5 liter per minute. Removal efficiency in three different states; plasma only, plasma /HZSM-5/TiO2 3%tw, and plasma/HZSM-5/TiO2 8% tw were assessed at the voltages of 4000 to 8000.
Results: In the current study, the removal efficiency of toluene vapors were 44.9, 75.36 and 66.68 percent for plasma, plasma /HZSM-5/TiO2 3%tw and plasma/HZSM-5/TiO2 8% tw, respectively. Photo catalyst with 3 weight percent showed the best removal efficiency. In all tests, the removal efficiency increased when the voltage increased and in 7000 volts it reached the maximum level. Therefore, adding photo catalyst to the plasma caused significant improvement in removal efficiency. Also, HZSM-5/TiO2 3% tw showed the best performance for toluene vapors removal.
Conclusion: According to the current study findings, using this combination in an industrial environment can be an effective way for Toluene vapors without the need for high temperatures. This combination can be proposed for other VOCs.
Ehsan Rezaieyan, Ebrahim Taban, Seyyed Bagher Mortazavi, Ali Khavanin, Hasan Asilian, Elham Mahmoudi,
Volume 12, Issue 2 (6-2022)
Abstract
Introduction: Micro perforated panel (MPP) absorbents promise the next generation of sound absorbers as they have significant advantages over other porous adsorbents. In this study, we will investigate the acoustic performance of MPP absorbents made of biodegradable polylactic acid composite reinforced with natural corkwood fibers (PLA/Corkwood) by 3D printing technology.
Material and Methods: First, the effective dimensional characteristics of the parameters were determined, then, all of the samples were fabricated by the Zortrax M200 3D-Printer using the FDM method. The normal incidence sound absorption coefficient of the samples was measured using an acoustic impedance tube according to ISO 10534-2 in the frequency range of 64 to 1600 Hz. Then the effect of four geometric parameters, including hole diameter, panel thickness, perforation ratio, and air gap depth, on the absorption coefficient was studied.
Results: The findings show that the SL-MPP 12 absorbent has the highest average sound absorption coefficient (SACA) with a value of 0.28, so that at a frequency of 804 Hz it has the highest sound absorption equal to 0.91. The parametric study found that as the hole diameter increased, the values of peak adsorption and average absorption coefficient were decreased. Increasing the MPP thickness causes the absorption peak to move towards the lower frequency range. Decreasing the perforation ratio increases the peak absorption values and the average sound absorption, and the frequency with the highest absorption also moves towards the higher frequency range. The resonant frequency also depends on the depth of the air gap behind the screen. Changes in air gap depth from 30 mm to 70 mm reduced the resonant frequency by more than 35%.
Conclusion: Using 3D printing technology, sustainable MPP can be fabricated with more quality and in less time than traditional methods such as mixing and heat pressing.
