Sharif Digital Repository

Due to safety critical applications of the embedded systems, reliability is one of the most important properties of these systems. Wireless networks also have error prone data transmission channels and limited power consumption. Therefore reliability and power conservation are two vital characteristics of the wireless network especially in embedded applications. Since achieving to a desirable level of data reliability is power consuming, we must consider a trade-off between power consumption and data reliability. In wireless networks power consumption can be categorized into: power consumption in wireless devices and power consumption in data transmission. For decrement of wireless devices... 

In recent years, there has been a trend toward outsourcing data to the cloud provider. These companies must tackle the data security challenges. Generally these parties are assumed to be honest but curious. In past years, the research communities have been investigating different solution to ensure confidentiality.
In addition to data confidentiality access and pattern confidentiality is a high-priority issue in some cases so. potential adversary should be unable to drive information from the observed access pattern to the outsourced data. Despite the fact that there are more investigation in the field of data confidentiality, concern over data security are the rise in outsourcing data,... 

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... 

People usually use trust and reputation when they encounter uncertainty in the nature. Graphs are good tools to model and analysis of trust’s problems. If we show human and computer agents by graph’s nodes and trust values by its edges, in literature, the output graph is so-called Web of Trust. Most recently, there are three major research areas in which trust is studied. First area is policy-based trust which uses policies, digital signature and authentication methods. Second area is reputation-based trust which uses reputation and social network tools to estimate trust where past interactions or performance for an entity are combined to assess its future behavior. Third area is trust... 

Peer-to-Peer networks are invented to enable participants (peers) to share their resources and find and use the shared resources of the others. So the main issue is the mechanism of finding granted resources of the other peers. In Peer-to-Peer networks, there is no central server to index shared resources of the peers. So peers should collaborate to provide a fully distributed mechanism for searching resources. Considering the huge size of peer-to-peer systems, it is apparent that efficiency of the search mechanism is very critical. In this thesis, to have efficient seach in Peer-to-Peer networks, we propose two approaches. Then based on these approaches, we propose the third approach to... 

With significant advances in software development technologies in recent years, it is possible to have complex software applications, wich include large number of heterogeneous software components distributed over a large network of computers with different computational capabilities. To run such applications, their components must be instantiated on proper hardware resources in their target environments so that all requirements and constraints are met and some quality of service parametesrs (e.g.,reliability, load balancing, etc) are also optimized. This process is called software deployment. For large, distributed ,component-based applications¬ with many constraints and requirements, it ... 

Today, peer to peer networks have become quite popular due to their ability to easy access to shared resources regardless of their location in World. In these systems files are stored at the end user machines which named peer, rather than at a central server, in contrast to the traditional client-server systems, files are transferred directly between peers. sending and receiving those data, occupy a large amount of the internet bandwidth. So, by improving the efficiency of these networks, the total efficiency of the internet will improved. These systems are usually constructed on the other networks such as TCP/IP as an underlay or physical networks. Despite of structure of peer to peer... 

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... 

Applying spoken dialogue systems (SDS's) is growing in the real life more rapidly because of the advances in the design and management of these systems. The traditional touch tone computer telephony systems are being substituted by the SDS's. In a typical SDS, the user speaks naturally to the system through a phone line and the system provides the required information or performs the required action. Banking and ticket reservation are typical examples of the prevalent SDS's. A spoken dialogue system has four units: automatic speech recognition (ASR), natural language understanding (NLU), dialogue management (DM), and spoken language generation (SLG). In this work, the first spoken dialogue... 

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... 

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... 

Due to the increase in size and complexity of software systems, choosing suitable software architecture is a fundamental issue. One of the most effective ways for designing and valuating software architectures is to adopt architectural styles. An architectural style is an approach for reaping the benefits of similarities that exist between various architectures. Adoption of architectural styles in the design process of a software system assures the employment of strength points of specifications that belong to each architectural style. However, selecting a suitable architectural style depends on different criteria. Therefore it makes the ... 

The development of a complex software needs an abstraction mechanism which is called Model Driven Engineering mechanism. In order to have a successful model based process, we need an appropriate tool such as version control systems to support our model-based process. On the other hand, developers need a mechanism to synchronize them with VCS systems. One of the concerns in modeling languages is the compatibility and the consistency of the models and modeling languages during their evaluation. the focus of the former researches was mostly on the consistency of the models during their evaluation, and to this end, lots of approaches have been proposed for keeping the consistency of the models... 

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... 

In this thesis an approximate method is proposed for analysis of two dimensional photonic crystal waveguides. In this method an equivalent impedance is assigned to photonic crystal regions and the waveguide region is modeled with a transmission line. Waveguide’s loss is also analysed and computed by this method. In other words the proposed method is able to determine the complex propagation constant of guided modes without computing any complex roots for dispersion equation. Although like any other approximate method, the accuracy of this method is dependent to some special conditions but it’s advantage over other numerical methods is its simplicity and its capability for waveguide designs.... 

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...