Sharif Digital Repository

Providing security for digital information in a communication channel is a challenge in the recent years. This is due to the strength of high-speed processing resources that can threaten the security and correctness of communicating information. Using steganography method, the secret information can be hidden in an innocent media that does not attract the attention of third parties. This research discusses about steganography in images. The main goal of this research is presenting a universal steganography scheme with high steganography capacity. Using this scheme the steganographer can embed every large secret data in images securely. The reasons for selecting the subject of “Improving... 

Hydroxyurea is an anticancer drug that is commonly used to treat chronic myeloid leukemia (white blood cell cancer in bone marrow), polycythemia vera (red blood cell cancer), sickle cell anemia, solid tumors, and in particular leukemia. In this research, in addition to analyzing all available methods for synthesis of hydroxyurea, the most economical method for synthesis of hydroxyurea which is Hantzsch method was chosen; then we synthesized hydroxyurea crystals using a precipitation or crystallization process. To do so, two hydroxylamine hydrochloride and potassium cyanate reactants have been used in the semi batch reactor. Since the reaction efficiency and purity of the synthesized... 

Cyclic distillation can bring new life in old distillation columns, by using a periodic operation mode that leads to significant benefits, such as increased column throughput, lower energy requirements and much higher separation performance. The design method for this type of column are reviewed. Among two design approaches, the Lagrangian one is selected, where equations are formulated as delay differential equations, moving from bottom to top of the column to determine feed tray location and total tray numbers. No rigorous design method is selected in order to calculate the column parameters.In this thesis, by defining an economic index that encompasses capital investment, operating costs... 

Due to the undeniable importance and applicability of both "batch processing" and "parallel machines" in service and industry, this survey strives to solve a real-world problem in which some identical parallel machine, capable of processing jobs in batches, are available. In batch processing the process of jobs starts and ends simultaneously. In real world the processing time of the batch is a function of some characteristics of the jobs in the batch. in this survey, for simplicity (as calculating the mentioned function is so difficult), we assume that the processing time of a batch equals the sum of the processing time of the jobs in the batch. we also have assumed that the capacity of a... 

Despite many advantages of granular sludge in anaerobic reactors (e.g. UASB), over the past few years research attention had turned towards developing aerobic granular sludge. Although much research is carried out on the formation of aerobic granules, less work is reported on how to enhance granules characteristics such as increasing in granule size, concentration, durability and stability. The aims of this study are to investigate the effects of cationic polymer on granule formation and the way to improve granule characteristics. For this purpose two SBR reactors (0.15 m diameter and 1.8 m height, R1 and R2) were used by feeding synthetic wastewater (diluted molasses, COD ranging from 1400... 

The existing thesis investigates the removal efficiency of ammonia from wastewater using natural zeolite, and the effects of various parameters on the removal efficiency. The importance of this research is due of the fact that ammonia is among the primary contaminants of wastewater. The common method of removing ammonia is biological processes that have a number of drawbacks. The ion exchange method could be a suitable alternative to the former method. Ammonia removal from wastewater was investigated through both batch and continuous experiments. In these experiments the initial ammonia concentration in the wastewater was chosen to be 1000 mg/L, 100 mg/L. The optimum ammonia removal was... 

The aim of this project is to inventigate and synthesize CaO-based nanocatalysts with metal promoters of magnesium and lithium by wet impregnation and coprecipitation methods, which are used in the transesterification reaction of canola oil and methanol. Sections of thesis include review of before researches , synthesis of nanocatalysts, catalyst characterization tests,and investigation of reaction under optimal conditions. In wet impregnation method, nanocatalysts were made with 5% by weight of lithium-magnesium on the basis of CaO and with different weight percentages of these two elements. In the co-precipitation method , catalysts with a combined base of calcium oxide/magnesium oxide ... 

Recent success of Deep Learning models, resulted in their evergrowing application in many fields. However these models usually require huge datasets, which can sometimes be hard to collect. One of the challenges related to medical data, is the Batch Effect; Medical data is usually gathered through multiple experiments. Each experiment might have a slightly different conditions than the other, resulting a shift in the data related to that batch. Batch effects can have more severe impact during testing time, as the shift in the data distribution could be bigger. Many methods have been proposed to reduce or remove the effect of external conditions on data distribution.Deep Learning models have...