فهرست مطالب r .dehghan

In order to plan and make managerial decisions for the development of wood farming in Guilan province, parameters such as area, distribution, and biometric variables of poplar trees were measured separately for each county. To conduct this research, the field of poplar plantations was located using the Global Positioning System (GPS) and measured with 100% inventory method. In each poplar plantation section, for every 2000 square meters, nine middle trees were measured for the biometric variables. The correlation between the characteristics of area and increment of trees with climatic indicators and soil was also plotted. According to the findings of this project, the total area of poplar plantations in Guilan province was 12,179 ha in 2018, with the highest belonging to Sowme`eh Sara county with 6,944 ha, comprising 11.8% of the county area. This county ranked first in poplar tree cultivation with the highest number and volume of trees. The area of poplar plantation was the lowest in Astara, Amlash, and Fouman counties. The highest mean age of trees was obtained in Rudbar and Tavalesh, while the lowest mean age and number of trees were obtained in Fouman county. The characteristics of the total number of trees, volume, and area of poplar plantation showed the highest correlation coefficient with climatic indicators and total nitrogen. The findings of this research can provide valuable basic information for monitoring the area of poplar plantations, planning and management decisions, and identifying areas suitable to poplar plantations for wood farming in Guilan province and the country.

While many studies have confirmed the effect of particle size distribution on the residence time in a reactor, the most employed models of continuous tank leaching process consider the residence time and particle size distributions as independent variables. In minerals processing field, no systematic study has been conducted on this issue yet. In this research, the relationship between the particles size and their residence time in a mixing tank has been studied. An empirical method for the determination of the residence time distribution function based on the inflow particles size distribution has been proposed. The relationship between the average size of one size fraction of particles and its residence time was obtained by mean residence time and parameter  (an empirical coefficient). Results showed that increasing the particle sizes resulted in a 50% increase in the mean residence time while  decreased from 0.95 to 0.3. Using the evaluated values of  the residence time distribution function of the inflow stream was determined. Including this function in the segregated flow model, the effect of the variations of the  value on the leaching performance was evaluated. Results showed that smaller values of  resulted in higher conversion value.

About 40 percent of total raw coal feeding to Tabas coal preparation plant, consists of particles in the size range of -50+6 mm. These particles are washed in a 700 mm (diameter) two-stage Tri-Flo dense medium separator. In order to understand the mechanism of separation, a laboratory setup including a transparent 70 mm Tri-Flo separator, tanks, pumps and the required instrumnets was designed and manufactured. In laboratory studies, some polymeric colorful tracers were added to the separator with different air core sizes, and were captured and counted in products’ tanks. The results indicate that probable error of separation (Ep) decreases while air core gets bigger. Relying the findings of laboratory studies, the industrial Tri-Flo was optimizaed using density tracers in the specific gravity range of 1.20 – 2.20 g/cm3, when the separator was treating raw coal. In this phase, we tried to change dense medium flow rate and internal tube diameter in the meaningful levels to evaluate the separator performance, rapidly. An increase of 9% in the production yield and 0.5% increase in clean coal ash were the results of increasing the internal tube diameter in industrial separator from 205 mm to 235 mm. 3% increase in the production yield and 1% decrease in the clean coal ash was also observed with increasing the medium flow rate. Similar to the results observed in laboratory separator, increasing the flow rate and pipe diameter leads to clearer separation in industrial separator. This research presents a successful use of the laboratory results for optimization of an industrial separator.

The effects of atmospheric pressure of the site of installation of a centrifugal two-stage heavy medium separator is of crucial importance because the pressure difference between the medium input and the sink output streams is adjusted by the back pressure rings. However, contrary to the dense medium cyclone, the raw feed ore into this separator is sluiced without pumping.  In this research, the effect of atmospheric pressure on the flow pattern inside the Tri-Flo separator is investigated using the computaional fluid dynamic (CFD) simulation. Therefore, the volume of fluid (VOF) model and discrete phase model (DPM) were used for the calculation of the diameter of the air core and the behavior of solid particles, respectively. Reynols stress model (RSM) was used for turbulence modeling. Simulations were performed in three different atmospheric pressure including 1, 0.86 and 0.64 atm, representing the site of installation at sea level and heights of 1250 meters and 3500 meters above the sea level, respectively. The CFD simulation results showed that the change in atmospheric pressure has some effects on the flow fields, macroscopic parameters and the performance of the Tri-Flo separator. The results of simulation were validated against the experimental data achived using the transparent laboratort Tri-Flo separator. The fluid velocity in output streams and the size and the pattern of air core were used for validation. The decrease in Ecart propale error (Ep) of the separator and increase in the medium recovery were observed, when the atmospheric pressure was decreased. However, the effects were in the margin of 2%. According to the results of this research, the Tri-Flo separator can be used in different elevations from the sea level, without serious problem in the operation regime.

Two-stage centrifugal separators are the last generation of gravity separators for the separation and upgrading of minerals. Gravity upgrading techniques are methods by which a mixture of particles with different dimensions, shapes, and masses can be separated by gravity, centrifugal force, and other forces by the flow of fluid, especially water (or air). The fluid flow inside such separators is always turbulent. The selection of a suitable turbulence model is an important stage for the prediction of the fluid flow pattern in numerical simulation. The purpose of this research was to find the suitable turbulence model for the prediction of hydrodynamic parameters in a two-stage centrifugal separator using computational fluid dynamics (CFD) modeling. For this purpose, multiphase simulation of the separator has been performed using five turbulence model including k-e, renormalization group (RNG k-e) and Reynolds stress model (RSM). Air core pattern, velocity distribution and partition curve of discrete phase were used for evaluation of the effect of turbulence model on the flow field. The results of the CFD simulation were validated using experimental data. The difference between the results of RSM simulation with the experimental results for fluid recovery, air-core size in the first and second stage of separator were 4.73%, 4.3% and 5.2%, respectively. The results of turbulence models of k-e and RNG k-e were not in accordance with the experimental results.

Due to the increasing growth of urbanization, vehicles are one of the most important environmental causes of air pollution in today's world..  With the increasing problems of air pollution and its environmental consequences due to lack of compliance with standards in manufacturing cars and their fuel consumption, awareness of the exhaust of cars and its comparison with environmental protection standards and technical examination is essential for controlling and reducing air pollution. Therefore, the present study was carried out with the aim of studying and comparing the amount of CO, CO2 and HC emissions from light vehicle exhausts in the period of 1383-1389 based on technical and environmental inspection standards in Shiraz. Also, the relationship between the year of construction of the car and the amount of output of these pollutants was discussed.

In this research, the amount of exhaust emissions (carbon monoxide, carbon dioxide and uncured hydrocarbons) from the exhaust of 858 vehicles included models Peugeot 206, GLX and Pars that were referred to the technical examination center during 5 months in Shiraz between the years 1383-1389 was investigated. Also, the relationship between the year of production and the amount of output of these pollutants was studied. Data analysis was done using SPSS software and Microsoft Excel software was used for drawing graphs.

The results showed that there was a significant and negative correlation between the year of manufacture of the vehicle and the reduction of CO and HC. As the year of construction increases, the amount of pollutants is decreasing. Also, this relationship was positive and significant between the year of manufacture and CO2. Also, the exhaust pollutants (CO and CO2) from the Peugeot GLX exhaust system were lower than Peugeot Pars and 206, and the lowest amount of HC was observed in Peugeot 206.

In general, the exhaust emissions of all three cars were at the standard Euro 2 and technical examination.

In recent years, there has been an increase in the trend for cesarean section. Due to surgical complications, financial costs and mother's long period of hospitalization, the normal way of delivery is suggested. Cesarean rate in Khorasan was estimated to be 28/1 in 1999, though the desired rate in the world was 15 per cent for 2000. This study was performed to define cesarean rate and causes and complications in Vali-e-Asr hospital in Birjand.

In this descriptive study, which cross-sectionally was carried out, 1500 pregnant women referring to Vali-e-Asr hospital were studied. A questionnaire in 4 portions was filled out at mothers’ bed, in delivery room, operation room, and women's ward. Data were analyzed by chi square test in SPSS software. (P<0.05)

From 1500 pregnant women in this study 895 (59.7%) had a normal delivery and 605 (40.3%) by Cesarean. There was a significant relationship between age, job, education level, number of pregnancies, previous delivery, live births, abortion number and the route of delivery (P<0.05). The comparison of mother's complications with delivery route was significant, but not for neonatal ones.

Cesarean choice rate is high and intervention programs are necessary to change women attitudes toward it and to increase the knowledge of painless delivery to reduce Cesarean.

Studying soil phosphorus fractions is useful in understanding soil pedogenesis as well as soil fertility. In this reseach, 20 soil samples were taken from different depths of 0-30 and 30-60 cm of upper-slope, mid-slope and lower-slope positions of four toposequences in arid (Jei and Ziar in Isfahan) and semiarid (Farokhshahr and Shahrekord) regions. In each toposequence, the soil depth was relatively low at the upper-slope position and increased toward the lower-slope. The soils in upper-slope and mid-slope were under scarce native vegetation where the soil in lower-slope was under farming activities. Soil phosphorus (P) fractionation was carried out using sequential extraction. The total soil phosphorus was in the range of 302-1135 with an average of 715 mg/kg. About 65-89% of total phosphorus were inorganic, and 11-35% organic. The amount of inorganic and organic P in the soil samples was in the range of 204-897 with an average of 571, and 70-238 with an average of 114 mg/kg, respectively. The amount of total, inorganic and organic P increased from upper-slope toward the arable lands and decreased from topsoil to subsoil in all toposequences. In the studied soils, apatite ( Ca10-P ), aluminum phosphates(Al-P), octacalcium phosphates( Ca8-P ), iron phosphates (Fe-P), iron oxides occluded phosphates( OC-P ) and dicalcium phosphates( Ca2-P ) were the major constituents of the soil inorganic phosphates, respectively.