An experimental evaluation of pre-yield and post-yield rheological models of magnetic field dependent smart materials

N. Mohammadi,M. J. Mahjoob,B. Kaffashi,S. Malakooti 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.9

The rheological behavior of field-dependent smart fluids in both the pre-yield and post-yield regimes is investigated. Typical viscoelastic and viscoplastic models are employed to model the fluids behavior. Viscoelastic models are used widely in the pre-yield regime. Viscoplastic models are also used extensively in both the pre-yield and post-yield regimes. Two smart fluids including a ferromagnetic nanoparticle fluid and an MR fluid are examined here. Using an MCR300 rheometer, the rheological properties of the fluids in both oscillation and rotational mode are measured. In the oscillation mode, the storage and loss moduli versus frequency are measured. In the rotational mode, shear stress, shear rate, viscosity and torque are measured. In the frequency domain, the pre-yield behavior of the ferromagnetic nano-particle fluid is modeled by Kelvin-Voigt solid model. Also, the three-parameter fluid model is used to model the pre-yield behavior of the MR fluid. Two viscoplastic models including Bingham-plastic and Herschel-Bulkley models are selected to model the rheological behavior of fluids in the time domain. Which model is more appropriate depends on the external magnetic field and the shear rate. Both models are used here to model the fluids’ behavior. The models properly predict the results observed in the experiments.

Reliability of Steel Cylindrical Pressure Vessel Dividers in the Presence of Corrosion: Experiment and Simulation

N. Habibi,S. Mohammadi,H. Ghafary 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.2

The Monte Carlo simulation method can easily provide an accurate estimate of the probability of failure. However, for complex engineering problems with a low probability of failure, it may be inappropriate to provide an inefficient estimate of the probability of failure. In this study, tests investigations were performed on pressure vessel separator plates made of marine steel A36 ASTM, which exhibited corrosion on all plates, and occurred during multiple operations. The results of the tensile tests show that the areas of fracture of the specimens were observed as follows: near the gage, in the allowable area, on the line of the gage, and outside. The data obtained here provide a quantitative understanding and benchmark of the tensile behavior of corroded plates. Strain energy and maximum force varied in corrosion rate ( ) between 10 and 24 fluctuated, while for > 24 decreased significantly. A series of simulations based on the Monte Carlo method was performed to determine the effects of corrosion rate and thickness variance on the overall behavior. The results of the two methods show that the values of the mechanical properties of the corroded specimens are scattered and follow a statistically normal distribution.

Evaluation of Sorghum (Sorghum bicolor (L.) Moench) Ability to Control Weeds in Corn (Zea mays L.)

G. R. MOHAMMADI,D. KAHRIZI,N. RASHIDI 韓國雜草學會 2009 Weed&Turfgrass Science Vol.29 No.2

In order to evaluate the weed control ability of sorghum in corn, a field study was carried out in 2006 at the Agricultural Research Farm of Razi University, Kermanshah, Iran. Sorghum plant materials were applied in three ways : (1) incorporated into the soil (at 2,000, 4,000 and 6,000 kg ha-1) mulched on the soil surface (at 2,000 and 4,000 kg ha-1) or sprayed as sorgaab (water extract of mature sorghum plants) one, two, three or four times during the growing season. Two controls(full-season weedy and weed-free condition) were also included. Full season weed-free condition increased height, the number of ears per plant, the number of seeds per ear, 100 seed weight and yield of corn by 67.9, 35.8, 66.1, 23.3 and 47.8%, respectively, as compared with weedy condition for all of the growing season. Among the sorghum treatments, the highest corn plant traits and the lowest weed dry weight and density were occurred when sorghum herbage was incorporated into the soil at 6,000 kg ha-1 or used as a mulch at 4,000 kg-1. However, corn yield and weed dry weight and density were not significantly influenced by one sorgaab spray, when compared with full season weedy condition. In general, this study revealed that sorghum plant materials applied in different forms can suppress weeds in corn field.

Sensitivity enhancement of AZO-based ethanol sensor decorated by Au nano-islands

H. Farajollahi,Z. Golshan Bafghi,E. Mohammadi,N. Manavizadeh,A. Salehi 한국물리학회 2020 Current Applied Physics Vol.20 No.8

Detecting the hazardous gases for monitoring air pollution and medical diagnosis make highly sensitive gas sensors appeal to many researches. In this paper, benefiting from unique properties of noble metals, Al-doped ZnO based Ethanol sensors were fabricated and characterized in three structures including Al: ZnO thin film, Silver and Gold nano-islands on Al: ZnO thin film. The Silver and Gold thin films turn to nano-islands after a simple annealing process. The XRD analysis of the sputtered Al: ZnO layer indicates the wurtzite crystal structure of the layer with a peak at (002) plane. Moreover, the sensitivity study reveals that Nano-islands of noble metals substantially affects the sensitivity of the sensors. The decorated Gold nano-island Al: ZnO Ethanol sensor has the highest response showing an amount of 45. The response of Al: ZnO and Silver decorated Al: ZnO sensors are virtually identical to all concentrations of Ethanol, whereas the Al: ZnO gas sensor with Gold nano-islands has the substantial sensitivity for different concentrations. In addition, the response times of the sensors are 85, 70 and 90 s for Al: ZnO, Al: ZnO with Ag islands and Al: ZnO decorated by Au islands, respectively. The recovery time of Al: ZnO sensor decorated by Au islands is about 23s, while the recovery time of the Al: ZnO and Al: ZnO decorated by Silver islands are 360 and 370s, respectively. Hence, the simple annealing process on the sputtered gas sensor with a thin layer of Gold makes nano-islands on the sensor which elevates the performance of Ethanol sensing due to the high sensitivity and sensitivity of the sensor.

Age-, sex-, and height-based blood pressure reference charts, Yazd children 6-18 years, Iran

ahmadi, Nastaran,Namayandeh, Seyedeh Mahdieh,Bafghi, Seyed Mahmood Sadr,Mohammadi, Mohammad Reza,Mirzaei, Masoud,Sarebanhassanabadi, Mohammadtaghi,Mehrparvar, Amir Houshang,Faraji, Reza,Nilforoshan, N The Korean Pediatric Society 2020 Clinical and Experimental Pediatrics (CEP) Vol.63 No.8

Background: Pediatric hypertension is the main cause of morbidity and mortality in pediatric populations. Purpose: To examine pediatric hypertension in a clinical setting, we used the percentile rank approach and defined hypertension as that above the 95th percentile. Methods: The present study was linked to the a national analytical cross-sectional community-based Iranian Children and Adolescents' Psychiatric Disorders (IRCAP) survey. The survey was nationwide and funded by the National Institute of Medical Research Development. The IRCAP survey included 31,000 children and adolescents aged 6-18 years in all 31 Iran provinces. The current study included 1,035 children and adolescents and linked the data of the risk factors of cardiovascular disease only in Yazd province via random cluster sampling. Results: Of the total participants, 456 (44.1%) were male and 579 (55.9%) were female. The mean age was 11.2±3.8 years (11.7±3.7 years for males, 11.0±3.6 years for females), while mean height was 146±20.0 cm overall, 147.2±22.0 cm for males, and 144.6±17.0 cm for females (P=0.009). The blood pressure distributions and percentiles were evaluated. Conclusion: Here we determined age- and height-specific 50th, 90th, 95th, and 99th percentiles of systolic and diastolic blood pressures in Yazd boys and girls using 10-cm height intervals.