Sharif Digital Repository

Magnetic bearings have been introduced in recent decades to overcome the problem of energy loses due to friction in bearings of rotating machinery. In magnetic bearings, the rotor is suspended by magnetic forces without any friction. These bearings are of the two types of passive and active. In Passive Magnetic Bearings (PMB), magnetic forces are generated by permanent magnets and have the ability to tolerate a small distribution. In Active Magnetic Bearings (AMB) magnetic forces are generated by electromagnets and have the ability to tolerate larger distributions than the PMB can. Since AMB is inherently unstable, it is necessary to use controllers to stabilize it. Due to the nonlinear... 

Electricity distribution companies always strive to operate the power network efficiently and reliably so that their network be able to satisfy the growing needs for electricity. To achieve these goals in a power network, a comprehensive asset management plan with a sound policy for inspection, periodic maintenance, replacement, and disposal of depreciated equipment is required. One of the high-risk sectors of the electricity grid is the insulation section of distribution and transmission lines. In recent years, composite insulators have been used more widely because of their desirable characteristics such as: hydrophobicity, lower price, and lower weight if compared with the another... 

In this study different kinds of solid phase microextraction fibers based on sol-gel technology were employed for extraction and pre-concentration of phenol in occupational air and oxadiargyl in plant and environmental samples. In the first work, a SPME method followed by on-fiber derivatization and gas chromatography-mass spectrometry detection (GC-MS) was developed for the analysis of phenol in the air. The application and feasibility of three different sol-gel based SPME fibers with different polarities, polar and non-polar poly (dimethylsiloxane) (PDMS) and polyethylene glycol (PEG), have been studied. Influential parameters such as fiber coating type, type of derivatization reagent,... 

Alzheimer's disease is the most common type of dementia, which has been recognized as the seventh most common fatal disease in the elderly over 65 years of age. Despite all the research done to recognize and treat this disease, so far there is no cure for this disease, and even most of the chemical treatments that are prescribed for Alzheimer's patients are only effective towards reducing the symptoms of this disease and lose their effectiveness as it progresses. Therefore, in the last two decades, in order to find a way to better understand and even treat AD, scientists have reached a concept called brain frequency stimulation, which can improve people's cognitive performance without the... 

Novel high-throughput device and their applications as the microextraction systems for pesticide multiresidue determination is the centre of this research. 96 extracting unit based on solid phase microextraction and micro-Solid phase extraction were constructed and applied for high-throughput extraction.
In the first work, a high-throughput SPME on 96-well plate together with gas chromatography-mass spectrometry was developed for the determination of pesticide residues in cucumber samples. A home-made Teflon block consisting ninety-six holes was constructed to 96 SPME fibers being positioned in. SPME fibers consisted of stainless steel rods with a 1.0 cm polydimethylsiloxane tubing... 

Thiomersal is an organomercury compound. This compound is a well established antiseptic and antifungal agent. It has been used as a preservative in vaccines, immuno-globulin preparations, skin test antigens, antivenins, ophthalmic and nasal products, and tattoo inks. Thiomersal is very toxic by inhalation, ingestion, and in contact with skin, with a danger of cumulative effects. It is also very toxic to aquatic organisms and may cause long-term adverse effects in aquatic environments.
Thiomersal's main use is as an antiseptic and antifungal agent in vaccines. In multidose injectable drug delivery systems, it prevents serious adverse effects such as the Staphylococcus infection that,... 

The purpose of the presented work entailed the development of a simple, high throughput sample preparation method for determination of a wide range of veterinary drugs at regulatory levels in milk, chicken meat and egg. pretreating the veterinary drugs include SPE pretreatment was combined with sample homogenization, acetonitrile and sodium sulphate salt extract and precipitate protein, n-hexane removal of fats, centrifugation and filtration. To proceed this goal, titania / octavinyl POSS (TiO2 / OVP) nanocomposite was prepared by sol – gel method and it was used to coat the surface of commercial cotton fabric. POSS supplies numerous organic and inorganic groups, facilitating the... 

Veterinary medicines are extensively applied in food producing animals for the treatment of various bacterial infections, so the risk of occurrence of unwanted residues in animal-derived food exists, which may have adverse effects on human health by directly causing disease via low-dose exposure and indirect harm via antibiotic resistance. The major challenges in determination of these residues stem from the complexity of matrix, as well as polar differences and low concentrations of them. This work aimed to develop a screening and quantification method for benzimidazoles, quinolones and tetracyclines residues in egg, milk and chicken muscle. For this, the sample was extracted with... 

During the recent years, manufactures and industries have paid attention to occupational health and safety of their employees. Formaldehyde is known as a probable carcinogenic agent and its large consumption made industries to consider it as a risk factor for occupational health. At vaccine production industries, Formaldehyde is used as disinfectant and stabilizer. In this study, a solid-phase microextraction (SPME) method based on kinetic and equilibrium calibration strategies was developed for monitoring of formaldehyde in the biologics production areas. The application and feasibility of three different sol-gel based SPME fibers with different polarities have been investigated. Two... 

The Use of peer-to-peer architectures instead of traditional client-server architecture can be beneficial in many aspects such as increasing scalability of the systems, enhancing fault tolerance in critical situations, extending the system resources and various other advantages. Nowadays, many applications are based on peer-to-peer architectures and as a result, a large portion of the internet traffic is produced by these applications. This has been a motivation to many researchers to focus on reducing the amount of this traffic while satisfying the content distribution demands. One of the main problems that can result in generating large amount of traffic and also long response times for... 

In today’s competitive world، web services have become more and more prevalent and their efficient discovery and composition in order to create novel functionalities is essential for variety of applications. Due to the large number of available services، the discovery of services is a difficult and time consuming task. Existing approaches in web services discovery and composition attempt to use simple web services while ignoring the use of once composed services. Reusing frequently used composite services can considerably increase performance of the entire system. Moreover، the advent of semantic web، as an effective solution of representing information interpretable by machines and none... 

Nowadays, the essentiality of appropriate modeling languages has become evident, and with the introduction of new concepts such as domain-specific languages, the need for systematic research on designing and engineering new modeling languages has increased significantly. Several modeling languages have been developed and employed over the years, but the area of modeling languages still suffers from the lack of a proper framework: There is a strong need for an engineering framework that specifies the detailed steps of language development, the input and output artifacts of each step, the techniques applicable to each step, and quantifiable methods for quality measurement. From a unified point... 

Peer-to-peer (P2P) computing is a popular distributed computing paradigm for many applications which in-volve exchange of information among a large number of peers. In such applications, large amount of data is distributed among multiple dispersed sources. Therefore, data analysis is challenging due to processing, storage and transmission costs. Moreover, the data rarely remains static and frequent data changes, quickly out date previously extracted data mining models. Distributed data mining deals with the problem of data analysis in environments with distributed data and computing resources. In this dissertation, we explore distributed data mining in different structures of P2P systems. In... 

Software Product Line is known as a process of developing family of the software together. The methods of building a software product line is trying to capture commonality and variety of this family of software and form a product line based on them. Commonality of this family of the software allows us reuse in every aspect of the development of software. Nowadays, software architecture as a one of the most important aspect of software engineering, plays major role in specifying the tasks and clearing the relationship between people. It can divide large and complex system to some sub-system and overcome complexity of the system. Software architecture forms a basis for communication among... 

Automation of the software development process is the software engineers' final goal, but with the current facilities and knowledge in software engineering, it is not possible to automatically generate the whole software. Usually all the software in a specific domain contain common behaviors, which by careful exploration of these common behaviors and automation of code generation in these sections, the cost and time of projects' execution can be reduced. According to Model Driven Development (MDD), the first step in software development is creating appropriate models. For creating models, metamodel is required; therefore, we need to create a specific motamodel for the chosen domain or use... 

One of approaches in software architecture design is using architecture styles or patterns. This approach is a suitable way for satisfying functional and nonfunctional requirements and also is cost effective. It is shown that this approach improves effectively quality of software systems. Whereas, choosing a suitability architecture style for complex designs depends on many factors and often one style cannot meet all the requirements, therefore, use of heterogeneous styles can be useful. Also, in software product line architecture design, we must combine different kinds of architectural styles to cover the problem domain and achieve better performance. Correct and accurate choice of...