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In this thesis we considered the effects of macro-economic factors on stock returns in order to estimate the risk free rate of return. For doing so, we used monthly returns of companies from 1383-1 to 1387-12.The sample of this thesis was consist of 48 companies which were present in stock market. Then the effect of 10 macro economic factors like Import, Export, Coin price, Oil price, M1, Inflation, Exchange rate, Index, Indext-1,construction permit on monthly stock returns was estimated for 5 years. The method which was used in this research was multi-factor model Arbitrage Pricing Theory (APT) and the method used was Factor Analysis.The aim of this research was to clarify whether co-movement of stock returns was the result of macro -economic factors or not, and also to estimate the risk free rate of return.The result of this thesis showed that co-movement of stock returns was due to different effects of macro- economic factors ,for inflation and indext-1 affected Tehran stock return during these 5 years ,and the estimated risk free rate of return of investment market was more than the risk free rate of return of monetary market.

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Abstract: Illogical limits of the stock prices have led to ambiguities in optimal resource allocations. Price limit prevents increase or decrease in stock prices with respect to the predetermined prices. There are different viewpoints on implementation of stock price limits. The negative or positive effects of implementing stock price limits haven’t yet been demonstrated. Those who advocate implementation of price limits claim that these measurements can reduce price volatility while not intervening in the transactions. On the contrary, the critics argue that price limit will make more volatility ( hypothesis of volatility extension), will prevent stock price to reach the balance level ( hypothesis for delay in reaching real price) and it will also intervene in transactions through limiting stock prices ( hypothesis of intervention in transactions). Different models and methods have been provided for measuring effectiveness of price limits in different global stock exchanges each of which are appropriate for certain conditions. To study the delay in reaching the real price, Z binomial test was used and Wilcoxon test was applied for studying intervention in transactions. 32 companies have been reviewed through the current research since 2000 to 2009. The results indicated that price limit can extend volatility and make delays in reaching the real prices. However, it doesn’t influence on intervening the transactions

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The main objective of this study is investigating the relevance of momentum and liquidity market status on short-term (6 and 12 months), medium-term (24 months) and long-term (60 months) periods. Statistical sample in clouded 270 firms that were accepted during years 82-85 in Tehran Stock Exchange, and are still working. The results showed that liquidity market status is a factor for separation of the market's effects on excess returns in different  periods of times. So that the momentum in the companies with high liquidity in 6 months formation and 6 & 12 months holding periods was positive, and the momentum in the companies with low liquidity in 24 & 60  months holding periods was negative. Also there was no significant difference between the profitability of momentum strategy in the companies with high and low liquidity.      

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There is a growing concern in countries around the world, including Iran, about the effects of extreme climate change, diversification, and events on food production, food security, and livelihoods. The link between climate change and food security in the Iranian food system is the subject of this article. This review, based on the available literature, used the food system approach to achieve a broader view on issues related to food security in Iran. To this end, this study investigated climatic challenges facing food security in Iran with a focus on two essential products in Iranians’ food basket, namely, wheat and rice: Decreased agricultural productivity, food losses along production and distribution chains, postharvest loss, low resilience of poor people in rural areas, and the prevalence of malnutrition among children. The results showed that in addition to measures, such as making food production systems resistant to climate change and the necessary changes in existing food systems to adapt to the consequences of climate change, achieving food security requires a long-term vision to transform the Iranian food system. Accordingly, it is necessary to develop a climate-smart agriculture system that encompasses all aspects of food system security. Except for investigating the productivity of some essential components of this food basket, the results showed that there are scant studies on the effects of climate change on the food system of Iran.