محمدرضا صمدی

One of the new and widely used polishing processes for the surfaces of cylindrical parts is the Magnetic Rotary Abrasive Polishing Process (MRAF). This process is done using magnetic force and rotational speed simultaneously and oppositely. In this process, the forces required for machining and surface polishing are applied to the surface of the workpiece through magnetic and rotational force. One of the capabilities of this process is the ability to finish the internal and external surfaces of various parts with a special geometric shape and axial symmetry. The purpose of this article is to investigate the mathematical model of the chip removal mechanism and surface roughness changes, as well as applied forces in the process, for an abrasive particle. In order to model and optimize process parameters, response surface method and analysis of variance have been used. Based on the presented mathematical model, it was observed that the parameters of rotation speed (S), working distance (w) and the dimensions of the abrasive particle (A) have a significant effect on the quality of the surface (Ra). Based on the surface response method, the lowest surface roughness value was obtained through a rotation speed of 700 rpm, a working distance of 1.5 mm and an abrasive particle with dimensions of 18 micrometers, which is equal to 43.64 nm and with the experimental value obtained from the tests, That is, 43 nm had an acceptable match and had a desirability level of 0.9959. The obtained results were in good agreement with each other in theoretical and experimental modes.

Polishing using nanoscale magnetic field (NMAF) is a new method for surface coating with nanoscale roughness as a mechanical process and is done by abrasive powder abrasion as a tool. The force required to move the abrasive particles is provided by a magnetic field that has a relative motion to the workpiece. This method can be used for polishing non-magnetic metal parts or non-metallic parts. One of the special features of this method is the reduction of thermal stresses to the workpiece and the lack of restrictions on polishing surfaces of the workpiece, which due to their geometric shape, the ability to work with conventional tools is difficult. Such as polishing of superalloys and hard metals, as well as for surfaces with special forms that can not be achieved by other methods to an acceptable level of smoothness. In this paper, using the nano-polishing mechanism, the polishing of cylindrical external surfaces of Inconel superalloy is investigated, so that the surface quality is improved at the nanoscale. To create a magnetic field, variable magnets with the ability to adjust the current intensity of the magnetic field have been used. In this research, aluminum oxide and silicon-carbide abrasive particles have been used and their combination.

Nowadays, aluminum and its alloys have extensive applications in marine and aerospace industrious owing to their excellent properties. Among these alloys, 5xxx series of aluminum alloys have also excellent corrosion resistance, high toughness and strength and also good weldability. Decrease in yield strength and also tensile strength due to the grain growth in the heat affected zone is of the main problems in the welding of these series of Al alloys. In this research work, gas tungsten arc weld joints in two modes i. e. direct current and pulsed current were compared in order to study the effect of this parameter on the microstructure, mechanical properties and corrosion resistance of weld joints. Also, the effect pulsed current parameters such as peak current and basic current were investigated. Microstructural evolutions and fracture surfaces of weld joints were examined by optical microscope and scanning electron microscope, respectively. It was found that the fracture behavior of all joints is in a ductile manner. Also, tensile test and electrochemical polarization were conducted in order to study the mechanical properties and corrosion behavior of weld joints.

Basically, corporate management is always forced to reform and improve production, marketing, innovation, and ultimately economic efficiency and efficiency among the units under its control, given the present and future economic conditions. One of the key ways in which factories can improve their economic status and increase their ability to compete with other competitors. It is through the use of creative thinking and system innovation that this would not be possible without the knowledge and support of intellectual capital. In this research, the elements and components of intellectual capital are considered as human capital, structural capital and relational capital, which are independent variables for each of the intellectual capital elements. Performance index (dependent variable): Profit is considered. The research method in terms of data collection is descriptive-correlational by covariance analysis method of structural equation model. 219 managers and experts of the statistical society were selected by probability classification method and a questionnaire containing 60 questions was given to them. After collecting the questionnaires, the data were analyzed using SMART PLS and SPSS22 software. Finally the relationships between intellectual capital indices were confirmed and it was found that structural and relational capital directly and human capital indirectly through structural capital had an effect on performance.

The most of medicinal plants seeds have dormancy under normal conditions, therefore, it is necessary to know the affective factors on seed dormancy and creation optimal conditions for their germination to extensive cultivation of medicinal plants. Dracocephalum kotschyi is an important Iranian endemic herbs which is extinting in the Lamiaceae family. This research was conducted in order to find the most effective treatment to break seed dormancy, which is one of the major problems cultivation on a large scale and rehabilitation in the natural areas. Experimental treatments including of scarification with sand paper, 95% sulfuric acid in 3 and 6 min and their combination, gibberellic acid (125, 250 and 500 μg ml-1), nitrate potassium (% 0.2 and %0.4 in 2 times) and also for moist chilling was at (5°C for 24, 48 and 72 hours) as compare to control (watering in 24 and 48 hours). The experiment was done base on the completely randomized design (CRD). The obtained results indicated that, there was a significant difference (p-value< 0.01) between in treatments of scarification with sand paper and 95% sulfuric acid on germination percentage, germination rate, vigor index, fresh and dry weight of the plumule and radicle. The results showed that sulphuric acid treatment in 3 minutes increased significantly seed germination as compare to control and other treatments. Obtained results represents that the presence of seed hard shell and high mucilage is a physical barrier and acts as a limiting factor in the germination of dragonhead by preventing the spread of embryos or by limiting the absorption of water and gas exchange. So, application of some treatments like scarification and hormonal treatment such as gibberellin could be improved the germination of dragonhead.

On of the most important problems in theology is the question that is it possible for humanbeing to gain Knowledge of the God? And what is the limitations of this Knowledge? considering the divine’s nature, names and attributes, which level is the subject of cognition?is this cognition with or without Intermediate?Despite that both sadra and Avicenna have some common ideas in this field, such as impossibility of knowing the divine’s nature, they have their own views about human’s cognition of god.This article discusses and critiques their views and argues for the correct answer with descriptive - analytical approach.