Sharif Digital Repository

Mobility is one of the most challenging issues in mobile Ad-Hoc networks which has a significant impact on performance of network protocols. To cope with this issue, the protocol designers should be able to analyze the movement of mobile nodes in a particular wireless network. In this paper, a new framework called Mobility Analyzer has been introduced for analysis and recognition of mobility traces. At first, the Mobility Analyzer acquires some mobility traces collected by GPS or generated with mobility simulators; then it calculates some mobility metrics which represent the movement behavior of the mobile nodes; finally it attempts to classify mobility traces into particular mobility models... 

Mobility is one of the most challenging issues in mobile ad-hoc networks and has a significant impact on performance of network protocols. Different kinds of mobility models have been proposed to represent the movement pattern of mobile nodes in mobile ad-hoc networks. These models attempt to capture various mobility characteristics existing in real movement of mobile nodes. In this paper, a new framework called Fuzzy Mobility Analyzer has been proposed to evaluate mobility models. At first, our framework categorizes mobility models based on their mobility characteristics into five classes; subsequently it uses mobility metrics to capture the mobility and graph connectivity characteristics... 

Subsonic wind tunnel experiments were conducted to study the effect of forced transition on the pressure distribution in the concave portion of contraction. Further more, the effect of early transition on the turbulence level in the test section of the wind tunnel is studied. Measurements were performed by installing several trip strips at two different positions in the concave portion of the contraction. The results show that installation of the trip strips, have significant effects on both turbulence intensity and on the pressure distribution. The reduction in the free stream turbulence as well as the wall static pressure distribution varied significantly with the location of the trip... 

Protective relay technologies have evolved from single-function electromechanical and static relays to modern multifunction digital relays over the past few years. Protection systems play a vital role in maintaining a desirable level of reliability in power systems. Thus, their own reliability should be evaluated and any cause of their malfunction should be fully comprehended. In this paper, a new reliability model is proposed that associates protection system failures to four main causes: 1) relay hardware, 2) relay software, 3) ancillary equipment, and 4) human error. In addition, this model can take other aspects of the protection system into consideration, such as human error during... 

Protective relay technologies have evolved from single-function electromechanical and static relays to modern multifunction digital relays over the past few years. Protection systems play a vital role in maintaining a desirable level of reliability in power systems. Thus, their own reliability should be evaluated and any cause of their malfunction should be fully comprehended. In this paper, a new reliability model is proposed that associates protection system failures to four main causes: 1) relay hardware, 2) relay software, 3) ancillary equipment, and 4) human error. In addition, this model can take other aspects of the protection system into consideration, such as human error during... 

Predicting latency between nodes on the internet can have a significant impact on the performance of many services that use latency distances among nodes as a decision making input. Coordinate-based approaches are among the family of latency prediction techniques where latency between each pair of nodes is modeled as the virtual distance among those nodes over a virtual system. This article proposes the Decentralized Coordinate System (DCS) as a fully distributed system that does not rely on any infrastructure support from the underlying network. DCS uses a two-phase algorithm: first, each host is assigned rough coordinates, then, the rough estimation is refined in a way that it gradually... 

With recent deregulation in electricity industry, price forecasting has become the basis for this competitive market. The precision of this forecasting is essential in bidding strategies. So far, the artificial neural networks which can find an accurate relation between the historical data and the price have been used for this purpose. One major problem is that, they usually need a large number of training data and neurons either for complex function approximation and data fitting or classification and pattern recognition. As a result, the network topology has a significant impact on the network computational time and ability to learn and also to generate unseen data from training data. To... 

To make the energy market reliable and transactions deliverable, transmission owners must provide required ancillary services that are critical to ensure transmission open access, and to maintain an acceptable level of power system security. Spinning reserve is one of the most important ancillary services required to maintain system reliability in case of occurring a contingency. By definition, spinning reserve is the unloaded section of synchronized generation that is able to respond immediately to serve load. Studies indicate that spinning reserve requirements have significant impacts on the energy market. A new spinning reserve market structure is proposed in this paper to best utilize... 

This work deals with waste heat recovery from a proposed direct internal reforming molten carbonate fuel cell (DIR-MCFC), including an integrated pre-reformer. In this regard, some advantages are attainable over exhaust gas recycling. For instance, due to low temperature in the pre-reformer, carbon deposition and coke formation resulting from higher hydrocarbons can be eliminated. In this study, the cathode outlet provides the heat requirement for the pre-reforming process. After partial heat recovery from the cathode outlet, the stream still has a considerable energy and exergy (352.55 °C and 83.687 kW respectively). This study investigates waste heat recovery from the proposed DIR-MCFC,... 

Wireless networks with the shared media require Medium Access Control (MAC) protocol that provides contention resolution mechanism. The design of MAC protocol in underwater sensor networks is a challenging issue because of limited energy source and high propagation delay. The most important goal of the MAC design for underwater sensor networks is to resolve data packet collision efficiently with respect to energy consumption. So, selection of MAC protocol is an important task because it has significant impact on the system efficiency. A suitable MAC protocol must consider some factors such as fairness, energy consumption, latency and throughput based on various applications. The bandwidth in... 

As the delay time and hence nuclei formation play a crucial role in the pathophysiology of sickle cell disease, MD simulation and molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) calculations have been performed on three systems of hemoglobin; namely dimer of hemoglobin with valine (Hb S), tryptophan (Hbβ6W), and phenylalanine (Hbβ6F) at β6 position. The structural changes due to these aromatic substitutions are investigated. It is shown that β subunits have significant impact on the differences between a dimer and other crystal structures. Transition from a dimer to polymer for Hb S system affects the donor molecule more than that of the acceptor. In the case of donor and... 

Fractures identification is essential during exploration, drilling and well completion of naturally fractured reservoirs since they have a significant impact on flow contribution. There are different methods to characterize these systems based on formation properties and fluid flow behaviour such as logging and testing. Pressure-transient testing has long been recognized as a reservoir characterization tool. Although welltest analysis is a recommended technique for fracture evaluation, but its use is still not well understood. Analysis of pressure transient data provides dynamic reservoir properties such as average permeability, fracture storativity and fracture conductivity.An infusion of...