Sharif Digital Repository

Pelamis is a semi-submersible device that can extract wave energy and converters that to electrical power. It has 5 cylindrical structure that connects through the joints. This device takes the shape of wave and the wave forces tubes to had angular relative motion together. The Main task of this device is to convert the angular movements of tubes to the Linear movement of pistons. External mechanism called the energy capture device are responsible for absorbing wave energy through angular movements, and then the internal mechanism, called the Power Take-Off, are responsible for converting this energy into the electrical power for use in the electricity grid. This device was designed and... 

Wireless Multimedia Sensor Networks (WMSNs) have many applications in survilient systems. In this kind of applications, although we have limited energy and computational power, we should provide minimal security to transfer data in such networks. These constraints are more crucial when we use multimedia that has more data for processing and transmission. Because of this huge amount of data, we must use compression for using less energy in both processing and transmission.
In some algorithms, it has been proposed to integrate compression and encryption in order to decrease time and power consumption. The proposed algorithm is several times faster than AES (Advanced Encryption Standard) or... 

Wireless Sensor Networks (WSNs) are rapidly emerging as an important area in mobile computing research. Applications of WSNs are numerous and growing, some of them are even highly critical, like military or safety applications. Security measures must be applied to protect the network from a variety of attacks. Since no intrusion prevention measure is perfect, intrusion detection becomes an important second wall to protect the network. WSNs have unique nature which is different from other kinds of networks. In this project, we examine the characteristics and vulnerabilities of WSNs and propose a new intrusion detection model to protect the network security. In this work we have not only... 

Knock is an abnormal phenomena in combustion engines and one the main limiter elements in increasing engine efficiency. From years ago, recognition and elimination of this phenomenon had studied by investigators and various approaches to anticipation had presented. One of the newest methods is using of property variety in air and fuel mixture with using technologies like Variable Valve Timing (VVT) system.
The purpose of this work is development a simple model in basis physics of 3 zone, homogeneous, ignition combustion with a partial kinetics model that this model can predict the knock phenomenon onset with good precision for various qualities of mixture. This study survey effect of... 

The explosive growth of battery operated devices has made low-power design a priority in recent years. Moreover, embedded SRAM units have become an important block in modern SoCs. The increasing number of transistor count in the SRAM units and the surging leakage current of the MOS transistors in the scaled technologies have made the SRAM unit a power hungry block from both dynamic and static perspectives. One of the key strategies for reducing power consumption is reducing the supply voltage to near or below the threshold voltage of the transistor. However, as supply voltage decreases to tackle the power consumption, the data stability of the SRAM cells have become a major concern in recent... 

In view of environmental problems and the limited energy supply, synthesis of new liquid fuel from coal or natural gas is becoming a hot research in recent years. Dimethyl ether (DME) is one of the most promising alternates of such synthetic fuels. In this project the kinetics of direct DME synthesis from syngas (H2 and CO) over the new bifunctional catalyst has been investigated in slurry reactor system. A new mechanism and rate law expression were established. The kinetic model has been fitted the experimental data, which has been obtained by other researchers. The new bifunctional catalyst was composed of Cu/ZnO/ZrO2 and Al-modified H-Mordenite zeolite. The calculated apparent... 

The purpose of this study is to increase the strength of metal and polymer compound combinations in the direction of this increase, the electrolytic plasma oxidation coating is applied and its effect will be checked to increase bond strength. Also, due to the failure in the polymeric side of the bonding, the effect of adding short fibers of carbon to polypropylene will be checked on the strength of the polymer and bond strength. The effect of current density at coating application, the presence or absence of short carbon fiber in the polymeric field and the formation of initial hole on aluminum alloy on bond strength was studied. For further analysis, the optical and electron microscopic... 

This thesis is devoted to the study of suitable functional frameworks for proving propagation of chaos and mean-field limit of nonlinear Vlasov-type equations for indistinguishable particles. The Kac model is a classic example and the motivation of this functional structure. On the one hand, Kac considered a spatially homogeneous gas, and on the other hand, he reduced the problem to one-dimensional collisions and dropped the conservation of momentum assumption. Therefore, he obtained a simplified version of the Boltzmann equation, which is named after him, the Kac equation. The main results which we study are quantitative estimates
on the decay of fluctuations around the deterministic... 

Energy conversion and storage as well as life sciences are among the areas of our daily life. Interest in carbon nanomaterials for energy storage systems such as supercapacitors has enormously risen due to their attractive electrical conductivity, chemical inertness, and charge storage capacity. Producing these nanomaterials with a simple, scalable, and cost-effective method is the major problem for commercializing them. The reduction of graphitic oxide is a versatile procedure to prepare 3D graphene. Despite many green methods, the dynamics behind ultrafast thermal graphitization have remained elusive. Here, we demonstrate an effort to understand the graphitization mechanism of graphitic... 

One of the the most fundamental questions in computability (recursion) theory is the exact structure of D and in particular that of R. Over the years, various efforts have eventuated in Degree ?eory, an interesting subfield of computability theory, which is concerned with various properties of these algebraic structures which have turned out to be extremely complex. Beyond any doubt, the most useful tool for proving theorems related toRis the Priority Method which is first introduced to solve the Post’s problem. Over the years, increasingly more sophisticated versions of the method have been used to prove complex statements about R. Roughly one may classify the priority arguments into three... 

Recent advances in storage and processing, have provided the ability of automatic gathering of information which in turn leads to fast and contineous flow of data. The data which are produced and stored in this way, are named data streams. data streams have many applications such as processing financial transactions, the recorded data of various sensors or the collected data by web sevices. Data streams are produced with high speed, large size and much dynamism and have some unique properties which make them applicable in precise modeling of many real data mining applications. The main challenge of data streams is the occurrence of concept drift which can be in four types: sudden, gradual,... 

Spam filtering is one of the large scale applications of machine learning. Much research has been carried out in the machine learning field with regards to spam filtering. Most of this work falls in the areas of batch learning or offline incremental learning. In batch learning, the learning process is carried out once on all the learning data. In applications such as spam filtering, in which the learning data is large in comparison to memory resources and data is generated in a stream, using incremental learning is required, in which the learning phase is repeated periodically. In each learning iteration of an offline incremental learning algorithm, a new set of data is learnt by the... 

There are a lot of methods for the settlement of the reserve power market which can ultimately lead to a pattern of consumption and generation for each of the participants of the power market. After this step, however, justified and logical methods should be utilized for paying the reserving costs to the participants as in a long-term it can optimize the economic conditions of the market which can result in getting more realistic bidding from the participants. The current methods used for paying the reserving costs are mostly locational marginal prices and pay-as bid approach. By the same token, for receiving the reserving costs from the customers, some consider the desired reliability level... 

Time delay generates exponential transcendental terms in characteristic equations. Subsequently, the applied methods are narrow to assess the stability map of delayed fractional-order systems with vanishing fractions. In this case, it is convenient to approximate these equations with its integer-order counterparts to design controllers or investigating features of the systems. But, delay can cause enormous differences between characteristic of these two equations. This study offers a method to survey analytically the stability of fractional-order time delayed linear time invariant systems with infinitesimal fractions. In this method, equations are transferred to an explicit expression which...