درخت حوزه‌های تخصصی

The purpose of this study is to develop portfolio optimization and assets allocation using our proposed models. The study is based on a non-parametric efficiency analysis tool, namely Data Envelopment Analysis (DEA). Conventional DEA models assume non-negative data for inputs and outputs. However, many of these data take the negative value, therefore we propose the MeanSharp-βRisk (MShβR) model and the Multi-Objective MeanSharp-βRisk (MOMShβR) model base on Range Directional Measure (RDM) that can take positive and negative values. We utilize different risk measures in these models consist of variance, semivariance, Value at Risk (VaR) and Conditional Value at Risk (CVaR) to find the best one as input. After using our proposed models, the efficient stock companies will be selected for making the portfolio. Then, by using Multi-Objective Decision Making (MODM) model we specified the capital allocation to the stock companies that selected for the portfolio. Finally, a numerical example of the Iranian stock companies is presented to demonstrate the usefulness and effectiveness of our models, and compare different risk measures together in our models and allocate assets.

Audit market concentration causes to decrease the scope of companies' au-thorities for selecting the audit institutions but instead it increases the power of auditors' market that it turns, leads to a decrease in quality and an increase in auditors' stress. The purpose of the present research is to study the effect of audit market concentration on auditors's job stress and audit quality of Tehran Stock Exchange (TSE) Listed Companies performed on a total of 97 companies between the years of 2013-2017. In order to evaluate the audit market concentration, the ratio of company's audit fees to total industry audit fees was used. The Accruals Quality model was also used to evaluate the audit quality. The results of the study showed that the audit market concentration had a negative and significant effect on the audit quality so that with the increase in audit market concentration, the audit quality is decreased. Also it was found that the audit market concentration had a posi-tive and significant effect on the auditors' job stress: it means that the in-crease of concentration on audit market as a result of time pressure can in-crease the auditors' job stress and thus the risk of financial statement assess-ment.

The multidimensional exponential Levy equations are used to describe many stochastic phenomena such as market fluctuations. Unfortunately in practice an exact solution does not exist for these equations. This motivates us to propose a numerical solution for n-dimensional exponential Levy equations by block pulse functions. We compute the jump integral of each block pulse function and present a Poisson operational matrix. Then we reduce our equation to a linear lower triangular system by constant, Wiener and Poisson operational matrices. Finally using the forward substitution method, we obtain an approximate answer with the convergence rate of O(h). Moreover, we illustrate the accuracy of the proposed method with a 95% confidence interval by some numerical examples.

In the first nine months of 2018, the triple increase of dollar price made the stock market an attractive place for speculation, especially for non-professional investors. Hence, this study was aimed to investigate the profitability of speculation in the foreign exchange market (dollar) and to compare it with investment in three indices of sugar, oil products, and basic metals. First, the conditional Sharpe ratio was calculated separately for these four assets. Then, six investment portfolios were developed for these four assets. The results showed although dollar speculation with mean daily return of 0.6% had the highest return among the ten investment assets, dollar speculation was ranked last, or tenth (0.096) in terms of performance and profitability by considering the standard deviation or daily conditional risk using conditional Sharpe ratio. Moreover, the results indicated that from among the six portfolios with equal weight, three investment portfolios consisting of merely Tehran Stock Exchange indices had a better performance than three investment portfolios comprising dollar speculation and each stock exchange index. It was also found that the risk of lack of capital diversification by investors was higher than that of accepting a higher-level risk.

The problem of desertion the effective and efficient staff and specialist staff is one of serious problem has been created for the organizations managers that seek to maintain, improve and utilize their human resources. Researchers believe that staff desertion will have a negative impact on the organization and not only reduce the organizational performance, but also increase the direct and indirect costs of staff desertion, such as transferring capabilities to competitors, increasing costs of hiring and training new staff, etc. The purpose of this study is to determine the effect of auditors' skeptical personality traits with considering the characteristics of organizational behaviour on job durability. For this purpose, the relationship between interpersonal trust, locus of control and presumptive doubt and neutral of professional skepticism and three characteristics of organizational behaviour, organizational commitment, perceived organizational support and organizational citizenship behaviour on job durability are assessed. The statistical society consists of all auditors of audit institutions that are the member of the Association of Certified Public Accountants who are working and not the organization's partners. The structural equation modeling has been used for analysis. The findings of the study show that auditors' skeptical personality traits did not directly affect their job durability.