f. vaezi

Many portfolio optimization problems deal with allocation of assets which carry a relatively high market price. Therefore, it is necessary to determine the integer value of assets when we deal with portfolio optimization. In addition, one of the main concerns with most portfolio optimization is associated with the type of constraints considered in different models. In many cases, the resulted problem formulations do not yield in practical solutions. Therefore, it is necessary to apply some managerial decisions in order to make the results more practical. This paper presents a portfolio optimization based on an improved knapsack problem with the cardinality, floor and ceiling, budget, class, class limit and pre-assignment constraints for asset allocation. To handle the uncertainty associated with different parameters of the proposed model, we use robust optimization techniques. The model is also applied using some realistic data from US stock market. Genetic algorithm is also provided to solve the problem for some instances.

Fresh leachate has a low pH and high amounts of BOD and COD which are mainly constituents with low weight molecular such as volatile fatty acids (acetic and propionic acids). Management and treatment of leachate is an important subject in sanitary landfill operation and performance.Th objective of this study is determining the efficiency of the integrated coagulation –flocculation and ozonation processes in fresh leachate treatment of Tabriz city.

Quantitive parameters of pH, BOD5, COD, alkalinity and TSS were studied based on standard methods.The study emphasizes of COD and TSS leachate removal.Alum, ferric chloride and PAC had been used as coagulants.

Results indicated the superiority of Ferric chloride at the dosage of 1 g/l in pH 10, which reduced 34% of COD and 54% of TSS.in the stage of ozonation the leachate sample coagulated by ferric chloride was treated by 3 g/h ozone gas at optimum pH and after 39 hours ozonation about 51% of COD and 18.2 % of TSS were reduced.

This study clearly indicates that there would be need to apply biological treatment (after coagulation – flocculation) and ozonation, various advanced oxidation processes and / or other treatment methods for further reduction of COD in leachate and meeting discharge standards.

As a result of the regulations on DBPs, interest in NOM removal is increasing and many water treatment plants in developed countries have started to measure the concentration of TOC in their finished waters. Promulgation of the rules will substantially increase these efforts in other countries too. Since the cost of TOC (and DBPs) determination was high, it was decided to study the traditional analysis of COD as a surrogate measure to detect the organic constituents in raw water and the extent to which optimized coagulation with ferric chloride can increase COD removal. The two water samples studied belonged to Karaj and Jajrood Rivers. For both samples the observed values of COD removal by coagulation at lower pH (about 1-1.5 pH values less than the regular pH) were about 85-95 percent without making water turbidity unacceptable. In order to determine the effects of organic content on coagulation, synthetic samples were also prepared with much higher COD values. Again, considerable increases in COD removal have been observed for most of these samples only by decreasing 0.5-2 pH value. The results indicated that a modified coagulation process without need to much increasing the amount of coagulant can be developed for these water samples.