Sharif Digital Repository

A novel Fe3O4/poly (aniline-naphthylamine) (ANI-NA)-based nanocomposite was synthesized by chemical oxidative polymerization process as a magnetic sorbent for magnetic solid phase extraction. The extraction efficiency of this sorbent was examined by isolation of rhodamine B (RhB), a mutagenic and carcinogenic dye from aquatic media in dispersion mode. The efficiency of the synthesized Fe3O4/copolymer composite was examined and compared with Fe3O4/polyaniline (PANI) and Fe3O4/polynaphthylamine (PNA) by quantification of RhB using spectrofluorimetry. Among them, Fe3O4/poly (ANI-NA) nanocomposite showed a prominent efficiency. The scaning electron microscopy (SEM) image of the synthesized... 

Inherently safer design is the new approach to maximize the overall safety of a process plant. This approach suggests some risk reduction strategies to be implemented in the early stages of design. There are different well-established strategies for making a process plant inherently safer. The benefits of applying these strategies on reducing the overall risk inside a plant are obvious. However, some of these changes are rejected many times because they appear to be too costly. But if the effects of applying inherently safer design strategies are investigated not only on the processing costs of a plant but also on the potential accident costs, the decision would in fact be different. In this... 

In the current status of the world production business, any action that can improve quality or decrease the price of products is very important to manufactures. Therefore, many studies had been conducted to do this. In production stages, the assembly stage includes 30% of production cost and up to 40% of production time. Therefore, optimization and design of the Production sequence of this stage are very important. This matter is more important in complicated and multi-segmental productions such as car manufacturing, the Aviation industry, and the shipbuilding industry. Also, optimization of the Production sequence could improve product quality. In this study, an algorithm has been purposed... 

In this research, we study one of the challenges in the field of software engineering, namely the detection of diplicate questions in Stackoverflow, the Q&A community of programmers. The works done in this area has problems such as complexity and reduced performance over time. The proposed solution is based on machine learning and modern representation learning methods. Representation is done with two approaches, domain specific learning and transfer learning. Fasttext and GloVe, the two word embeddings used in domain specific learning, and in transfer learning, the embedding of the universal sentence encoder has been used. Support vector machine and multilayer perceptron used as... 

In this research, we have studied optimization of culture medium and process factors for high alkaline protease production from Bacillus subtilis ATCC 6633 for detergent usage. Five parameter soy bean meal, initial pH, agitation rate, MgSO4, CaCl2 were selected for more studies. At first, one-factor-at-a-time method was applied to investigate effect of each factor separately. Then, optimum condition for maximum protease production was achieved using Minitab software Box-benhnken procedure. According to results, high protease production was seen in soy bean meal, 35 (g/L); MgSO4, 1 (g/L); CaCl2 , 1.5 (g/L); initial pH, 7; agitation rate, 150; inoculum ratio, 12% (v/v). The activity of the... 

For supersonic inlets with reduction of mass flow ratio to a specified value self-induced oscillations know as Buzz would occure. Study and suppression of these oscillations are categorized in the field of inlet stability. In this work performance and stability of a supersonic inlet is studied experimentaly. Also a flow control mean is examined for stability and performance improvement. Investigation of the effect of bleed location as a key parameter for this flow control method is the main goal of this study. The model used is an axisymmetric mixed compression inlet. Experiments were done in 3 freestream Mach Numbers of 1.8, 2.0 and 2.2 with application of bleed and in no-bleed condition.... 

In this project the RGO/Ag2O/g-C3N4 nanocomposite was synthesized, and characterized by different technique such as SEM, XRD, and FT-IR. Then its photocatalytic activity was investigated. The degradation percent for Acid-Blue 92 by this photocatalyst was estimated 81 in 45 minutes. Afterward, the photocatalyst activity was determined in different pH including 4, 7, 10. The best result was for pH=7. Then, the increasing concentration of dye were investigated and the results show that by increasing the concentration of 10 to 30 ppm, the photocatlytic activity decreased. Photocatalytic degradation process of AB92 were also carried out at different amount of photocatalyst. The mechanism of... 

The quality is the last word of customer satisfaction concept. The structure and the main goal of many of large and small companies have been formed with systems aggregate related to process and product quality. Whereas quality is not achieved only under the protection of inspecting and controlling, then the quality management standards have been designed and produced to control all the activities and organization effective processes. Quality management standards in auto industries have been developed with increasing of customer desire and their severity simultaneously. Which the set of some standards such as ISO 9000, QS 9000, VDA, … and the most ISO TS 16949 requirements have been used.... 

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... 

Based on the latest statistical figures, more than 50 billion Rials worth of medical equipment exists in Iran’s medical centers. In spite of this, Breakdown maintenance is used in all hospitals, which means that the equipment is utilized as long as it is not out of order and only in such a situation, i.e. a breakdown, the necessary repair operation is conducted on the equipment. In fact, no maintenance is carried out to prevent a breakdown, while the “prevention from breakdown” concept has long been introduced in the majority of industries in many countries including Iran and its positive impacts are undisputable. This thesis aims at proposing a solution for the implementation of a “planned... 

Semantic technology provides an abstraction layer above existing computational environments, especially the Web, to give information a well-defined meaning. Moving toward semantic-aware environments imposes new security requirements. One of the most important requirement is the authorization and security policy inference based on the existing semantic relationships in the abstract (conceptual) layer. Most of the authorization models proposed for these environments so far are incomplete and their inference rules are not guaranteed to be consistent, sound, and complete. To have a sound and complete system for policy specification and inference, in this thesis, a family of modal logics, called... 

Applied pi calculus is a variant of the pi calculus with extensions for modeling cryptographic protocols. In such a calculus, the security guarantees are usually stated as equivalences. While process calculi provide a natural means to describe the protocols themselves, epistemic logics are often better suited for expressing certain security properties such as secrecy and anonymity. These methods studied in this work to investigation the verification of privacy properties in security protocols. And finally, a new approach is introduced to bridge the gap between these two approaches: using the set of traces generated by a process as models. In this method an epistemic logic has constructs for... 

In the secure data outsourcing scenario, verification of the reply of an unreliable server includes assessing the authenticity, completeness and it’s integrity. In this thesis, an efficient method, with emphasis on freshness, has been introduced to evaluate the correctness of the replies from a server. It takes in hand different application needs, inherent differences in the data, and different update mechanisms. This method evaluates freshness by using timestamps alongside the data being out sourced. Due to the requirement of verifying not only the freshness of the response, but the correctness of the timestamps as well, two general methods for evaluating and verifying the responses were... 

Growth of tools that ease sharing information and resources in social networks can cause privacy issues for the users. Protecting user’s personal information against unauthorized access is a crucial task, and it is considered as a first step for preserving user’s privacy in such networks. Policies, access control rules, and the way rules are applied to online social networks are issues that are less investigated and most existing frameworks have used simple models. Growth of users joining social networks and significant volume of resources shared in these networks make such environments suitable for using semantic technology. Semantic technology is used for modeling various resources, users,... 

EOQ and EPQ models have been among the most important and commonly used techniques for about 100 and 60 years respectively .But, they are involved in some assumptions that sometimes prevent them from being implemented in real situation of industry and production. One of these unrealistic assumptions is that all of items received or produced are of perfect quality. In order to overcome this constraint and make the mentioned models closer to the real environmentsome researches have been done. To this end,following the previous attemptsin this project we assumed to have destructive inspections and existence of imperfect and rejected items after rework. In our models, considering 3 circumstances... 

Access control, which is the process of mediating every request to resources and data maintained by a system and determining whether the request should be granted or denied, plays an important role in the system security. The existing of non-monotonicity property in a deduction and decision making process means that some of the previous deductions or decisions may be retracted by adding new information and premises. Based on the definition, in a non-monotonic access control system, adding new information or access control rules may invalidate some of the previous conclusions (permissions/prohibitions). The requirements such as decision making based on the imperfect information, supporting... 

Portfolio is a collection of different stocks for investment. The investors' objectives in portfolio formation are to get the highest return against exposure to the lowest risk. Portfolio Optimization Problem is one of the most complicated problems in investment and finance. It may be simply explained as follows: Let's imagine a set of N stocks for selection. We would like to see what percentage of the total amount of investment should be dedicated to each stock to maximize portfolio's total return and minimize its total risk.
Portfolio Optimization Problem is a NP-Hard problem and generally there exists no polynomial-time deterministic algorithm to find a precise solution to such a...