درخت حوزه‌های تخصصی

Portfolio selection is one of the most important financial and investment issues. Portfolio selection seeks to allocate a predetermined capital (wealth) over one or multiple time periods between assets and stocks in a such way that the wealth of investor (portfolio owner) is maximized the risks are minimized. In the paper, we first propose a mathematical programming model for Portfolio selection to maximize the minimum amount Sharpe ratios of portfolio in all periods (max-min problem). Then, due to the uncertain property of the input parameters of such a problem, a robust possibilistic programming model (based on necessity theory) has been developed, which is capable of adjusting the robust degree of output decisions to the uncertainty of the parameters. The proposed model has been tested on 27 companies active in the Tehran stock market. At the end, the results of the model demonestrate the good performance of the robust possibilistic programming model.

Purpose: In the shadow of separation of the ownership from the control and the problem of representation arising from it in the modern business world, there is a need to pay attention to the CEOs' approaches toward takeover as decision makers in this area. Managerial entrenchment is considered as one of the consequences of separation of ownership from control that explains the difference between the incentives in the corporate management and causes a disturbance in internal control as a communication mechanism between the corporate's performance and the capital market. Paying attention to operant conditioning behavior like tournament incentives as a functional behavioral stimulus in CEOs reduces the profit-seeking attitudes among them and increases the effectiveness of the corporates' performance mechanisms in disclosing financial reporting. The purpose of this research is to study the relationship between the managerial entrenchment and the internal control weakness by operant conditioning behavior theory test. Design/methodology/approach: In this research, 95 companies listed in Tehran Stock Exchange were evaluated between  2013 and 2018. Considering the duality of internal control assessment, logistic regression in SPSS software was used in this research. Findings: Results of the research showed that there is positive and significant relationship between the managerial entrenchment and the internal control weakness. But there is a negative and significant relationship between the tournament incentive and the internal control weakness. Moreover, it was found that the negative relationship between the managerial entrenchment and the corporates' internal control is mediated by the tournament incentive. Originality/value: Considering that little attention has been paid to motivational issues of the CEOs under the representation theory over the past few years, the present research attempts to investigate managerial entrenchment approach with the effectiveness of internal controls through analysis of the operant conditioning behavior theory to provide more reliable experimental results for the investors and the shareholders.