مطالب

This study aims at getting a better performance for optimal stock portfolios by modeling stocks prices dynamics through a continuous paths Levy process. To this end, the share prices are simulated using a multi-dimensional geometric Brownian motion model. Then, we use the results to form the optimal portfolio by maximizing the Sharpe ratio and comparing the findings with the outputs of the conventional model. To examine the robustness of the results, we have evaluated its performance for different investment horizons and various volumes of price information over a long period (approximately twenty years) in the Tehran Stock Exchange (TSE). Findings indicate that within the trading dates spanning the interval 24-Mar-2001 to 19-Sep-2020, the return of the portfolios obtained from applying this simulation scheme for maximization of Sharpe ratio is (244% on average) higher and their risk (standard deviation) are lower (1227% on average) than those realized by the conventional methods. Additionally, a comparison of the simulation approach with a performance of the actual market portfolios indicates that the Sharpe ratios of the simulation method are higher (0.055% on average) than those resulting from the total market performances. The results of the stochastic dominance test show that our proposed strategy has a first-order stochastic dominance (FSD) over the conventional one and market portfolios, that means at each level of cumulative distribution, the Sharpe ratio of our method is higher, and as FSD test makes no assumptions about the curvature of investors' utility functions, these results do not depend on the degree of risk aversion of investors, and as long as investors prefer a higher Sharpe ratio, they would be better off if they follow our proposed strategy.

The present study investigated the relationship among teachers 'mindsets and their perceptions of students' behavior, learning, and achievement, their interpretations of students 'behavior, and their strategies to increase students' motivation through a qualitative approach and a descriptive phenomenological design.The target population of this study includes all female primary school teachers in District 1 of Yazd city. Initially, 18 teachers volunteered to participate in the study, according to the call. Then, they completed mindset questionnaire and after evaluating the answers and determining teachers’ mindset, 5 teachers were purposefully selected for a more profound and more extensive study. The data were collected using Dweck's Mindset Questionnaire (2000) and Semi-structured interviews. Content analysis was used to analyze the data and the results showed that the relationship between teachers 'mindsets and their perceptions of students' behavior, learning, and progress could be traced through the categories such as fixed mindset's teacher, growth mindset's teacher, and six factors including stereotypes, performance interpretation, evaluation, instruction, motivation, and responsibility. In general, it can be said that teachers 'mindset affect the way, they interpret students' behavior, learning, and success, it is influential on teachers' instructions, evaluations, and responsibilities in the teaching process as well as the type of activities that they use to increase students' motivation. Furthermore, the results showed that teachers' mindsets are intertwined with cultural assumptions; and teachers can be made aware of cultural challenges by increasing their level of knowledge and modifications of their mindsets.

The present study aims to predict the role of learning approaches, studying strategies, metacognitive strategies, and reflective thinking on students’ academic achievements. A cross-sectional analytical study was carried out in Iran. The statistical population encompasses the all 5000 students at Roudehen Islamic Azad University throughout 2020-2021. According to Morgan's Table, the sample size was estimated to be 384 persons. Five standard questionnaires including studying strategies, learning approaches, metacognitive strategies, reflective thinking and academic achievement were used for data gathering. Structural equations based on partial least squares were used to analyze the data. The results showed a moderate relationship between learning approaches and metacognitive strategies while a significant relationship was observed between learning approaches, studying strategies, and reflective thinking (P<0.05). There was also a weak relationship between learning approaches and academic achievement. Beside, a moderate relationship was observed between metacognitive strategies and academic achievement, and a significant relationship was revealed between reflective thinking and academic achievement. Numerous factors affect academic achievement. Managers and families by recognizing these variables and providing appropriate conditions could smooth the rate of success for students.