Sharif Digital Repository

The classical economic batch quantity (EBQ) model assumes that all produced items have a perfect quality. But in real-life production systems, generation of defective items is inevitable. A portion of these defective items is considered to be scrap , while the other is assumed to be reworkable and reworking them can reduce costs and increase productivity. In this thesis we have studied the economic batch quantity for a single stage production system with rework and scrapping . We want to satisfy the customer demand and minimize total costs of the system like set up costs , production costs , rework costs , holding costs , shortage costs and scrapping costs . In the first chapter of this... 

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... 

This research attempts to develop the optimal solution for an inventory problem consisting of a single machine which produces items some of which may be defective. We assume that no shortages are allowed and all defective items are to be reworked. Setup cost for rework and waiting time of defectives are considered. This research consists of two different parts. In the first part we consider two different policies where in the first policy in each cycle after the regular production the machine is setup for the rework of defectives of the same cycle. In the second policy several cycles constitute a period. All the defectives produced in the period are reworked in the last cycle of that period.... 

In the present study , operation of a laboratory scale sequencing batch reactor (SBR) was evaluated to treatment of synthetic wastewaters containing ethylene glycol. Studies carried out with a plexiglass bioreactor whith effective volume of 18 lit.Aeration was supplied via two air diffusers that set at the bottom of the reactor. Synthestic wastewater containing ethylene glycol and molasses as carbon source and other nutrient such as diammonium hydrogen phosphate as phosphor source and urea as nitrogen source for biological activities was composed at the laboratory. To optimization of this reactor three parameters – aeration time, chemical oxygen demand and sudden change in arganic loading... 

Recently, The Earth has become warm rapidly over the past few years. This global warming is not only caused by natural phenomena, and further increased by humans and the amount of greenhouse gases in the atmosphere. Around 40 to 50 percent of energy consumption is related to information technology and communications. However, the rapid growth of electricity consumption in data centers, in addition to increased costs, data center challenges faced serious environmental pollution and more greenhouse gases. Use of renewable energy and reducing electricity costs in data centers are the important subjects for researchers around the world. Many researchers provide solutions to reduce environmental... 

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... 

Fed-batch fermentation is a valuable and cost-effective method for bio-based production of various products such as ethanol, which has various applications in various industries.In recent years, bioethanol production has been given special attention in many countries. For this reason, the mathematical modeling of production of these products is very important for their optimal and cost-effective production. Given the transient and dynamic nature of fermentation and its specific complexity, mathematical modeling of fed-batch bioreactors is difficult and complicated. In this research, an unstructured model was used to predict the production of ethanol from blackstrap sugar cane molasses based... 

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... 

Almost all of the animal slaughter is done in slaughterhouses. Environment concerns about slaughterhouse industries have been increased as increase in their production. In this study, a DAF+SBR system was used for treatment of industrial slaughterhouse wastewater and efficiency of this system was evaluated.In DAF, we used anionic polymer and PAC as coagulant. We reached best composition in 2 ppm of AP and 200 ppm of PAC. After that DAF system run in different pressures to estimate the best operational pressure & A/S. Best operational pressure and A/S is 4 bar and 0.038. After pretreatment, biological treatment by using SBR reactor was carried out. The results of the SBR reactor showed that... 

In this study, a semi-structured model for the growth and production of lactase in an aerated bioreactor by Kluyveromyces marxianus, growing on cheese whey, was developed. Three modes of culture, consisting of batch, fed-batch and a controlled-release system were investigated. Modeling was based on three metabolic pathways, representing the growth of Kluyveromyces marxianus. Lactose and oxygen consumption, cell growth, and also lactase and ethanol production rates were determined in the model. Induction was considered as the governing mechanism for enzyme production. The model showed good agreement with the experimental data in batch and fed-batch cultures. Controlled-release system is a... 

In recent years, utilization of hybrid attached and suspended growth system for modification of conventional activated sludge systems has attracted a lot of attentions. Nowadays, with development of urban areas and also introducing new emerging contaminants and as a result an increase in the influent loading of wastewater treatment facilities, the importance of upgrading and retrofitting available facilities have been highlighted. Conversion of Sequencing Batch Reactors to Sequencing Batch Biofilm Reactors is a viable solution for overcoming these problems. Eventhough several researches have been conducted on removal of different contaminants through these systems, the information about the... 

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... 

Steganography is method for communicating confidential information through a non-trustworth in way which hides the existence of communication. For improving the security of steganography statistical detectability must decrease as such as possible. Despite the fact, that the quality of the relation between statistical detectability and amount of distortion engendered by embedding is still an open problem, problem of detectability reduces to problem of management of pixel embedding in order to minimization of distortion. As in wet paper coding methods, an optimum (or approximately optimum) algorithm proportioned to Pixel-cost has been offered, the current problem of steganography is to find... 

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... 

Obtaining polymers with desired properties is very important from industrial point of view. Weight average molecular weight and polydispersity are two important polymer properties. It is also important to obtain a high monomer conversion. In this thesis production of polyvinyl acetate is considered. Under special conditions, the vinyl acetate reactor dynamics become oscillatory which makes the reactor control difficult. For obtaining polymer with desired properties, an objective function which includes weight average molecular weight, polydispersity and monomer conversion has been defined. Then by minimizing this objective function the optimal temperature trajectory is obtained. In this... 

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 Atomic Energy Organization of Iran (AEOI) has launched a program of low level waste management. This program also includes waste produced at Uranium Conversion Facility (UCF) of Esfahan. The liquid waste, which was generated during the operation of plant and concentrated in lagoon, was characterized for the development of the treatment process. The aim of this study was to recovery of uranium content of liquid waste in the lagoon. The recovery of uranium has the advantage of saving this valuable metal and the avoidance of unacceptable discarding solution to the environment. Uranium may be recovered from an aqueous solution by precipitation, solvent extraction and ion exchange.... 

Feature Extraction is an inseparable part of many machine learning algorithms. The extracted feature from the input data, while preserving the label information as much as possible, should make label inference more feasible than the input data itself. Additionally, in many machine learning, information theory, and privacy problems we have another constraint on eliminating sensitive, confounding, or unwanted information from the feature. That is why the problem of feature extraction with information regularization (preserving desired information and removing unwanted one) becomes an important issue that has been considered from different aspects, inter-connecting various fields.In this... 

consumption of which (especially azo dyes) have been increasing nowadays, causing the increase of textile wastewaters. Usually, these wastewaters contain an immense number of dyes, and if these dyes release in the environment especially in waters, they cause some problems, such as the change of watercolor as well as taste, and affect creatures' lives severely. Moreover, If the dyes are left untreated in aquatic ecosystems, they can remain in the environment for a very long time, resulting in harmful and irreversible effects. Azo dyes are classified as mono, di-, three, azo dyes due to their bonds. Because dyes are increasingly used, nowadays, different methods are developed for the treatment... 

Increasing in insider threats of the organization, made it necessary to use a security solution to investigate anomalies within the organization. Diagnosis of insider anomalies is based on examining the behavior of any entity, whether employees or systems of the organization. Entities are classified into different categories based on reported events. The high consumption of resources, the creation or elimination of entities, and the variability of their behavior over time are among the major challenges in diagnosing insider anomalies. In this research, while defining the process of diagnosing insider anomalies, a possible solution is presented considering the above challenges. In the...