مرتضی رفیعی

The reprocessing tailings of iron ore processing plants is important from economic (as a secondary source of iron) and environmental points of view. The aim of the present study is to determine the appropriate method for recovery iron from the tailings of Balestan iron ore processing plant (located in the northwest of Iran). For this purpose, after taking samples from the tail piles of this plant, a representative sample was selected, and chemical, mineralogical, size distribution, and bond’s work index analyses were performed on it. The total iron grade in the tailings was measured to be about 10%, of which 8.5% was identified as magnetite mineral (with a degree of liberation less than 40%). The d80 value of the sample was 7 mm, and the bond index was measured as 11.84 (kWh/ton). To determine the appropriate method for iron recovery, pre-processing with magnetic drum, grinding, and Davis tube tests were performed. With the magnetic pre-processing of tailings with a particle size of 0-10 mm, under a field of 2000 G and in a dry method, about 80% of the load entering the drum with a total iron grade of 5% was transferred to the tailings. 20% of the input load with an iron grade of approximately 24% was recovered to the concentrate. In order to remove the gangue minerals and enrich the pre-processed concentrate, stepwise grinding and separation had the best results. Comminution was done in two stages to produce products with smaller dimensions of 250 and 45 microns, respectively. Magnetic separation was also done in three stages with 3000 G, and two stages of separation with 1000 G, which finally resulted in a concentrate with a total iron grade of more than 66% and iron recovery of 44.88%.

In this paper, using Arnowitt-Deser-Misner (ADM) decomposition formalism, we first obtain a neutral black hole solution for consistent $D\to 4$ Gauss-Bonnet gravity. Then, we study its thermodynamic properties near the critical point by employing new formalism of thermodynamic geometry (NTG). More precisely, critical exponents of the number density difference $\Delta n$, the isothermal compressibility ${{\kappa }_{T}}{{P}_{c}}$, the normalized intrinsic and the normalized extrinsic ${{K}_{N}}$ curvatures are calculated near the critical point for the small/large black holes phase. Our findings show that the critical amplitude of the normalized thermodynamic curvatures are independent of the Gauss-Bonnet coupling values that indicates their universal feature.

Informational efficiency is an influential variable in financial markets that affects the flow of capital and the optimal allocation of resources. There is extensive literature on the factors affecting information efficiency and our aim in this study is to examine the reports of analysts as one of the factors affecting this variable. For this purpose, the effect of analysts' reports in the Tedan system in general and also in a classified way on the information efficiency of 291 companies listed on the Tehran Stock Exchange during the years 2015 to 2020 was studied using multivariate regression. The information efficiency in this study has been calculated by two methods of variance ratio and Fama and French three-factor model and the results indicate that the Tedan system reports do not affect the information efficiency of Tehran Stock Exchange companies.

Companies are always looking for ways to pay lower tax, through tax avoidance. By highlighting the similarities and differences of companies, financial statement comparability increases the users' will be able to identify unusual transactions of companies and reduces managers' willingness to tax avoidance. Therefore, the purpose of this study is to investigate the effect of financial statement comparability on tax avoidance and also to examine the moderating role of market competition in this regard. For this purpose, using multiple regression analysis on panel data, the data of 110 companies listed on Tehran Stock Exchange are analyzed during the period 2013- 2018. The results show that the financial statement comparability as a governance mechanism prevents managers' opportunistic behaviors including tax avoidance. The findings also indicate that the negative relationship between comparability and tax avoidance is less severe in firms in highly competitive industries. This result supports the view that competitive pressure can increase managers' incentives for tax avoidance by providing more cash to invest and cope with the competition.

In this paper we give an introduction to the ideas of quantum thermodynamics, using only basic concepts from quantum and statistical mechanics. Then, we discuss the framework of non-equilibrium processes in quantum systems and introduce how to calculate quantities such as work and irreversible entropy in these processes. We then apply these results to the problem of atom-cavity system while their interaction describe by Jaynes-Cummings model with both weak and strong atom-cavity coupling. Here, we introduce the concept of quantum thermodynamics of close quantum system and so by considering a good cavity, coupling of cavity modes with its reservoir has been omitted.

In this research side ratio effect of ultrasonic guided waves in a bar with rectangular cross section is investigated and wave structure is calculated and plotted. The motion of ultrasonic guided waves in the mentioned bar is considered as a three dimensional problem. In the homogenous equation system that is obtained to satisfy stress free surface boundary conditions, the ratios determinant of this system should equal zero. So, the frequency equation is obtained. The real roots of this equation are extracted and frequency spectrum, phase and group velocity diagrams and wave structure for longitudinal, torsional and bending waves are plotted by a written computer program by Matlab. Increasing cross section bar side ratio shows when the frequency increases the longitudinal and torsional waves phase velocity decreases and bending waves phase velocity increases. Also, for some modes replacing particles on the bar surface is considerable and for some others is negligible.

Although it is obvious that nutrition has a clear impact on incidence, prevention, and treatment of many diseases, it has not been addressed properly in medical education. Therefore, physicians’ educational needs assessment is the first step of improving physicians’ skills in nutrition and diet therapy. It is a cross-sectional study. In this study, a focus group was hold. Then essential topics for training physicians was developed using the job analysis approach (Including determining the tasks; sub tasks; skills and items that can be corrected through training). Five main tasks that must be learned were achieved. They were nutritional status assessment, patient’s data analysis, determining the diet suitable for patient’s condition, planning the diet therapy, its implementation, and evaluation. 19 sub tasks were defined for these main duties. There was a well consistency between our findings and earlier studies around the world. These results can be used to raise the nutritional knowledge of general practitioners whether through academic courses included in their curricula, or continuing education programs.

The advance in educational sciences has demonstrated the effective role of behavioral theories in changing individual's knowledge, attitude, and habits. Therefore, in order to have efficient and effective training about nutrition especially in group education sessions, applying curriculum development principles in determining educational content is inevitable The problems and obstacles in having effective nutrition education in units dealing with nutrition education especially in group sessions includes: lack of effective models and strategies for nutrition education, relying only on routine diets and providing different and unreliable information by different members of the treatment team for the patients. These problems motivated us to present this article in order to attain three general objectives. First, introducing general principles for education and group counseling in order to enhance the efficacy of nutrition education second, investigating factors affecting the quality of nutrition education through pointing to some important subjects and the third, providing a clear description for some behavioral attitudes and their related learning activities which are effective in nutrition education. This work explains that achieving educational objectives for making proper changes in patient's behavior is due to development and designing an appropriate educational model and guide. In such model, the structure of educational sessions, the procedure for nutrition education, the educational content, the educational strategies, and learning activities are based on curriculum development principles in which related behavioral elements have been considered.

Work function and surface energy per unit area were calculated in the framework of density functional theory (DFT) with Linearized A ug mented Plane Wave Plus Local Orbital method in full potential for a clean symmetric slab of silicon containing two (top and bottom) surfaces. The surfaces were theoretically modeled using supercell technique by stacking a variety of silicon layers along (111) crystallographic direction. In order to make the slab symmetric, two equivalent amounts of vacuums were added on the top and bottom of the Si(111) surfaces. In order to simulate the interface between lead and silicon, thin films of Pb were deposited on the prepared Si(111) surfaces. The calculations were performed in the absence and presence of spin-orbit coupling (SO) for the three phases of top site, T1, and fcc, T4, as well as hcp, H3. Our calculated total energies in agreement with experimental measurements show that the T1 phase, for which Pb atom is located along the Si atom of the first silicon layer, is the most stable phase. For the interface of Pb/Si(111) work function and energy formation were then calculated obtaining the most stable top site phase into account. The Si-Pb bond in the interface has been determined to be sigma.

Hypertension as a major coronary artery disease (CAD) risk factor is more prevalent in Iran. In recent years, the effect of antioxidants in reducing CAD and their risk factors has been considered. Therefore, this triple blind placebo-controlled clinical trial was performed to determine the effects of antioxidant vitamin E on blood pressure in patients with mild hypertension. 70 subjects with mild hypertension (SBP: 140-160 mmHg, DBP: 90-100) and without secondary hypertension who were referred to hypertension unit in Isfahan Cardiovascular Research Center were recruited. All subjects were aged between 20 and 60 years old with only one cardiovascular risk factor. They were divided randomly into two sub-groups of supplement or placebo. Two sub-groups were matched for confounding factors such as job, age, sex, religion and education level. Supplement group was received 200 IU/day vitamin E tablet and placebo group was received a placebo tablet per day for 27 weeks. At the beginning and at the end of the study, the vitamin E level was measured using Hansen & Warwick method by flourometric method in all subjects. Blood pressure and heart rate were measured at the beginning; during and at the end of the study by a physician using the same sphygmomanometer. At the end of the study, it was found that the vitamin E supplement decreased 24% systolic blood pressure compare to 1.6% in placebo group (p<0.05. Diastolic blood pressure was decreased 12.5% in supplement and 6.2% in placebo group after 27 weeks (P<0.05). It is concluded that 200 IU/day vitamin E supplement as decreases mild hypertension may be the cause of increasing long term availability of nitric oxide and its influences to monitor blood pressure.