حسین جعفرزاده

In the present investigation a new severe plastic deformation method called accumulative channel-die compression bonding (ACCB) was adapted for fabrication of Al1050-carbon nanotube (CNT) composites. Microstructure and mechanical properties of Al1050 matrix material and synthesized composites were analyzed using SEM and tensile testing. The obtained results showed that the average grain size of matrix is reduced to 7 and 4 μm after one and two passes of ACCB respectively. Processed composites and Al1050 showed a limited homogeneous plastic deformation indicating the limited work hardening capacity due to the high dislocation densities developed during ACCB process. Also, the tensile strength of Al1050-CNT composites was increased with increase in deformation passes. It was demonstrated that different mechanisms are responsible for improved mechanical properties including the increase in dislocation density and reinforcement fraction and grain refinement by plastic deformation. Fractured surface were showed a combination of ductile and brittle failure during tensile deformation.

In this research, fuel nozzles of GE-F9 turbine were tested, and fuel flow was measured using a Nozzle Layout device, which was designed and manufactured by Pardad Kameh Sanat Company. Then, the layout of nozzles was suggested by the special software of the device based on a specific algorithm, and it was installed on the turbine. The temperature spread was evaluated as the most important result of this research. The results show that by selecting a set of 14 out of the 30 initially provided nozzles and then using the layout recommended by the software, it is possible to reduce the gas flow difference by 2% and the temperature spread by 20 ℃. However, using two sets of nozzles out of the 30 provided can reduce the flow difference of the nozzles to 6% and 9%, respectively. In addition, with the help of the Nozzle Layout software, the temperature spread can be maintained below 28 ℃.

In this study a new severe plastic deformation method named noncircular thin section cyclic extrusion–compression (NCTS-CEC) is proposed for processing ultrafine-grained noncircular thin section beams. In this technique, the total length of noncircular L shaped section is passed through a neck zone and experiences severe plastic strains. Therefore, the high amount of accumulated plastic strain could be imposed by repeating the number of process cycles. In the first section of study, the AM60 Magnesium alloy is inserted into die and deformed by punch in different cycles. The observations by optical and SEM microscopes showed the formation of about 5 μm fine grains from the initial value of 75 μm after processing by two cycles of the NCTS-CEC. Also, the mechanical properties including yield strength, UTS, elongation and microhardness are evaluated at different cycles of NCTS-CEC processing. The obtained results showed the increase of yield strength and UTS to 136.9MPa and 286.7 MPa from the initial values of 89.5 MPa and 227.3 MPa, respectively. The Vickers microhardness is increased to 89HV from the initial value of 54HV at the end of second cycle. Also, the elongation of processed sample is increased to 14.4% from 11.3% due to texture evolution, grain refinement and breakage of brittle eutectic phases at the end of second cycle. The cellular automaton (CA) finite element method was implemented to simulate the process to predict the microstructure evolution of AM60. The obtained results from cellular automaton finite element (CAFE) and experimental methods were in good agreement.

Background and Aims :

Considering the importance of balance and the prevalence of genu varum in soccer, this study evaluated the role of lower extremity corrective exercises on dynamic balance improvement and knee deformity in teenage football players (youth footballers). 

Methods :

This semi-experimental study was performed on 24 male soccer players aged 15-17 years with genu varum deformity (more than 5 cm knee distance), who were divided into two groups randomly. Collis for measuring the knee distances and the star balance test for dynamic balance were used in both groups. After six weeks of corrective exercise with traband (three times a week) in the training group and sport-specific activities in the control group, all measurements mentioned above were repeated in both groups. Analysis of covariance for balance and Mann-Whitney U test for knee position were used with a level of significance less than 0.05.

Results :

The results showed the significant positive effects of the exercise program on the knee position (P=0.002) and dynamic balance variables (ant: P=0.002, med: P=0.004, post: P=0.005, posterolateral: P=0.006, and other directions: P˂0.001) and balance improvement and knee distance decreasing were found in the training group.

Conclusion:

 It seems that six weeks of traband training exercises can improve dynamic balance in soccer players by reducing the knee genu varum deformity.

In this study the radial-forwad-backward extrusion of axially joint cup shaped AM60 magnesium alloy part is investigatd. In the experimental tests, the cylindrical AM60 alloy samples were prepaed and pressed by a punch into the die cavity. In the next step, the initial and extruded samples were investigated in terms of microstructural evolution and mechanical poperties variation. The microscopic observations showed the significant grain refinement of AM60 is occurred at the end of extrusion proessingwhere the fine grains in size of ~7μm are obtained from the initial value of ~75μm. Also, the Vickers microhardness is increased to 88Hv from the initial value of 56 Hv. The obtained results of uni-axial tensile tests showed the increase in yield and ultimate tensile strength to 142.6 and 290.3 from the initial value of 93 and 230MPa, respectively. The extruded sample elongation is incresead to 13.4% from 10% due to texture evolution, grain refinement and breakage of brittle eutectic phases. The macro and micromechancal based cellular automaton (CA) finite element method were implemented to simulate the process to predict the microstructure evolution of AM60 during extrusion processing. The cellular automaton finite element(CAFÉ) and experimentally obtained results were in good agreement. The effect of some important parameters including friction coefficient, gap thickness and height and die corner radius are studied on the variation of maximum forming load, microhardness values and grain size.

By the fast growing of electronic related industries, the demand for application of high strength with high conductivity materials is getting increased. In this paper, the accumulative compound extrusion is proposed as a severe plastic deformation method to produce UFG pure copper. An initial copper billet is placed in the die. In the first half- cycle the billet is pressed against the fixed mandrel by an upper punch which results in radial and forward flow of material. In the second half-cycle the billet is regained it's initial shape by pressing down punch. The accumulated plastic strain in each cycle of ACE processing is computed by analytical method and the obtained results showed significant amount of imposed plastic strain. The microstructure evolution during ACE processing was significant grain refinement of 110-240 nm from the initial grain size of 39µm at the end of second cycle. The microhardness examinations showed the increase of ACE processed Hardness to 98HV from the initial value of 57 HV. Also, the results of tensile tests showed the increase of yield and ultimate tensile strength by the factor of 2.07 and 1.13, respectively at the end of ACE second cycle. The flow behavior of material was simulated using FEM in DEFORM 2D software and the model predictions were in good agreement with the analytical results. The electrical conductivity examinations of the ACE processed samples showed the UFG pure copper with high strength and good conductivity in contrast with the alloyed copper parts.

A four-level inverse Y-type atomic system with a microwave-driven field contained in a unidirectional ring cavity is proposed for controlling the optical bistability behavior with application on all-optical switching. Two circularly polarized components from a weak linearly-polarized probe beam are interacted separately by two transitions of this medium. A coherent coupling field derived another atomic transition. Under the steady state condition, we can control the occurrence of the optical bistability by modulating different parameters, such as the probe detuning ( ), the electronic cooperation parameter (C), the magnitude of electromagnetic field (B), and left- or right- handed circular polarized beams. Also, it is found that the stable output field of the optical cavity can be controlled by adjusting the intensity of the input field. It is demonstrated that the transmission coefficient of two orthogonally polarized beams at different frequencies can be achieved by adjusting the magnitude of the external magnetic field. It is found that the threshold of the optical bistability can be controlled by the magnitude of the external magnetic field. Also, it is shown that the optical bistability can be converted to optical multistability by switching the two orthogonally polarized beams. In this paper, in the case of the steady-state and transient response, we investigated the effect of external magnetic field on optical bistability of a four-level atomic system in the presence of strong coherent laser beam. Here, a laser probe signal consists of two left- and right- handed circular polarized beams which are interacted by two different transitions. The optical system provides a new experimental method to test optical bistability theory.

The agricultural sector in the West Azerbaijan province is faced with problems such as lack of capital and investment. Therefore, non-governmental funds for agricultural investment are a suitable solution for correct injection of funds to the agricultural sector. The purpose of this research was to study the effects of Agricultural Supporting Fund in the West Azerbaijan province. The research methodology was a descriptive – survey. The statistical population included 173 organizations of fund shareholders from whom 120 samples were determined by using the Kerejcie and Morgan table. The sampling and selection technique used for choosing the sample society was the stratified random sampling technique. The main tool of data collection was simple random sampling. The main tool of data collection was a questionnaire whose validity and reliability was confirmed by experts and Cronbach's alpha coefficient was between 0.712 to 0.935. Data were analyzed by using the SPSS (V.21) software. The R-factor analysis was used to explain the effects of the agricultural supporting fund on agricultural development in the West Azarbaijan province. The results of factor analyses showed that the effects of Agricultural Investment Fund in the West Azerbaijan Province can be classified in 5 effects that include; Economic effects, Social effects, Production effects, Skill effects and Educational effects. These items explained 71.42% of the total variation related to the Agricultural Investment Fund effects in the West Azarbaijan Province.

The objective of this study was a comparative evaluation of 20-year old plantations of Alder (Alnus subcordata C.A. Mey.), Chestnut leaved Oak (Quercus castaneifolia C.A. Mey.), Maple (Acer velutinum Bioss.) and Cypress (Cupressus sempervirens var. horizontalis) with the adjacent mixed broad leaved stand from qualitative and quantitative point of view. The study area is located in Darabkola, east of Mazandaran province in the Caspian region. One sample plot, each 1 hectare was selected in every plantation as well as in the natural stand. A total of 5692 trees were measured by full callipering; thestudied factores were diameter at breast height (dbh), height and qualitative haracteristics of trees. Also the physico-chemical properties of soil were studied in all treatments. The differences of the studied factors between the treatments were significant, statistically (p>0.01). Analysis of quantitative characteristics showed that natural forest and plantation of Alder were the most promising followed by Maple and Chestnut leaved Oak. From the qualitative point of view, alder and maple plantations were the most promising stands, while the Cypress plantation showed the worst results