JOURNAL OF IRANIAN ASSOCIATION OF ELECTRICAL AND ELECTRONICS ENGINEERS
Year:2012 | Volume:8 | Issue:2|Papers Count:7

We study the capacity of point-to-point erasure networks under a restricted form of network coding to which we refer as spatial network coding. In this form of coding, the nodes can not perform coding on successive packets which are received from one incoming link. The coding at a node is restricted to the packets received at the same time slot from different incoming links to the node. In other words, the temporal aspect of coding is absent. We prove that the capacity of a unicast session under spatial network coding is the statistical average of the minimum cut of the random graph corresponding to the erasure network. Then, we consider a network with a complete, directed and acyclic graph in which the nodes are erased independently. We prove that the capacity of the network under spatial network coding is the same as its capacity under general network coding. This shows that temporal coding has no improving effect for this network. Finally, we compare the capacities under different coding schemes for the complete graph with the edges that are erased independently.

In this paper a new inpainting scheme applicable to images with wide missed regions is presented. The proposed method is based on a new modification of the well known geodesic path image inpainting algorithm. Furthermore, to achieve a high-quality inpainting preserving details and textures, the image is decomposed firstly into texture and structure sub-images. Then, each sub-image is concealed based on a suitable technique and the final inpainted image is created. To evaluate the effectiveness of the proposed method, a comparative study with two basic methods over 30 images of different contents is performed and the results are reported. The experimental results confirm the effectiveness of the proposed method comparing with other methods, especially in the cases of images with wide missed regions.

This article is introducing a new controlling scheme for islanding operating of inverter-based distributed generations. That in this method load protection at the time of connection to the network and islanding operation is completely intended. Moreover, the islanding detection algorithm which is based on ROCOF relaying, for detecting islanding phenomenon is provided. The algorithm is also equipped with synchronization block that at the time of network retrieval would be able to reconnect the upper network to the distributed generation. It is necessary to mention that all the simulations and tests are carried out in the MATLAB / Simulink environment. Provided method has security and flexibility and will have no interference with operation of voltage regulation instruments in the distribution network.

In restructured power systems, generation companies should offer a power - price curve to the market operator to participate the auction. The proposed bidding curve has a considerable impact on the unit profit, especially in pay as bid markets. The optimal bidding curve depends on the final market clearing price which is uncertain in the stage of bidding. This paper proposes a novel approach for optimal bidding strategy considering the probabilistic nature of forecasted market clearing price. Numerical examples show satisfactory results in comparison with previous approaches.

Nowadays in order to increase the reliability and other special aims, the power networks are exchanged to the large and interconnected networks. In such networks, the relays setting and coordination is complicated and needs to determine break points. Break points are the initial points in coordination process and in pervious works, different methods are proposed to finding them in interconnected networks. In this paper, a method proposed to determine suitable break point set, considering some parameters such as pilot protection, Short circuit level, This method determines minimum break point set using genetic algorithm. After obtaining the solutions, the coordination is fulfilled using the obtained break point set and the break points are modified considering the coordination criteria.

In a realistic and large power system, the overcurrent relay coordination problem considering different network topologies and different location of faults is stated as an optimization problem with a large number of constraints. In this paper, a new index is proposed to detect and remove the inactive inequality constraints in relay coordination problem. This index is defined for each relay pairs, as the ratio of the variation of fault current passing through the primary relay to the variation of fault current passing through the backup relay. The proposed index is independent of the overcurrent relay characteristics and current and time multiplier settings of the relay, which is the most significant feature of this index. For IEC relay characteristic, it is shown that without the solving the coordination problem, the proposed index can distinguish the active and inactive inequality constraints. The 14-bus and 30-bus IEEE test systems are used to verify the performance of the proposed index. The presented results show that greater than 90 percent of the inactive constraints can be detected and removed from the set of constrains by using the proposed index.

In this paper a compact current-voltage model for MOSFET-like Carbon Nanotube Field Effect Transistors (MOSFET-like CNFET) is presented. To model these devices the one-dimensional drain/source current equation obtained from Landauer approach must be solved self-consistently with the equation relates the Fermi surface and carrier concentration. Also, numerically solve of the integral over density of states and Fermi function is necessary. This calculation is a little complex. In this paper, by studying the behavior of this integral in all regions and employing its functionality to Fermi surface we show that it can be approximated with a quadratic equation. This approximation results in a compact current-voltage model in both sub-threshold and above threshold which shows good agreement comparing with numerical one.