Sharif Digital Repository

Non-recursive and explicit expressions for calculating the number of ways to distribute n indistinguishable balls into m distinguishable bins with different capacities have been derived. Similar expression for the special case where bins have the same capacity was previously reported in the literature. Theses expressions can be used to study network graphs with grid structures. In this line, we have derived some topological properties of meshes, furnishing some expressions to calculate the surface area and volume of radial spheres in the mesh network. © 2003 IEEE  

The main contribution of this paper is to introduce a novel non-Lipschitz protocol that guarantees consensus in finite-time domain. Its convergence in networks with both unidirectional and bidirectional links is investigated via Lyapunov Theorem approach. It is also proved that final agreement value is equal to average of agents' states for the bidirectional communication case. In addition effects of communication time-delay on stability are assessed and two other continuous Lipschitz protocols are also analyzed  

The star graph, as an interesting network topology, has been extensively studied in the past. In this paper, we address some of the combinatorial properties of the star graph. In particular, we consider the problem of calculating the surface area and volume of the star graph, and thus answering an open problem previously posed in the literature. The surface area of a sphere with radius i in a graph is the number of nodes in the graph whose distance from a given node is exactly i. The volume of a sphere with radius i in a graph is the number of nodes within distance i from the given node. In this paper, we derive explicit expressions to calculate the surface area and volume in the star graph.... 

Grid-based networks (or grids for short), such as meshes and tori, have been the underlying topology for many multicomputers, and have been extensively studied in the past as a graph topology. In this paper, we investigate some topological properties of grids without boundary wrap-around (meshes) and with boundary wrap-around (tori). In particular, we study the problem of finding the number of nodes located at/within a given distance from a given node (surface area/volume) in the network and derive some expressions for computing such a number. Furthermore, we provide similar expressions that improve on previous results already reported in the literature for some special cases of grids,... 

As the infrastructure-centric model of peer-to-peer streaming, recent overlay construction schemes compose a hierarchical topology of peers by grouping them into clusters. There is a server in each cluster that receives data from the source and relays it to its cluster members. In this paper, we propose an alternative infrastructure-centric peer-to-peer framework called BAHMO that constructs a hierarchical multicast tree. BAHMO does not utilize server bandwidth and rely only on peer bandwidth for data transfers. It achieves both the stability of the infrastructure-centric model and the bandwidth efficiency of the fully-distributed model. Bandwidth assignment for inter-cluster data transfers... 

Overlay networks have been an active area of research for the past few years. The control overhead and the recovery from failure are the two important issues in the topology aware embedded overlay networks. In this research, we have introduced an enhanced version of the NICE protocol, called resilient NICE (R-NICE) that reduces the control overhead significantly. Furthermore, by saving the join path for an end host, the time and overhead of rejoining for isolated nodes have also been reduced. This will cause the clusters and consequently the overall network to become more stable and the effect of a node failure become localized. Our experimental results have confirmed the superior... 

In this paper, we introduce a new class of interconnection networks for multiprocessor systems which we refer to as Stretched-Hypercubes, or shortly the Stretched-Cube networks. These networks are obtained by replacing an edge of the well-known hypercube network with an array of processors. Two interesting features of the proposed topology are its area-efficient VLSI layout and superior scalability over the traditional hypercube network. Some topological properties of the proposed network are studied. In addition, an area-efficient VLSI layout for the stretched-cube is suggested and some comparisons between the proposed network and previously studied networks such as the star and hypercube... 

The star graph, as an interesting network topology, has been extensively studied in the past. In this paper, we address some of the combinatorial properties of the star graph. In particular, we consider the problem of calculating the surface area of the star graph, answering an open problem previously posed in [12]. © 2005 IEEE  

Hypermesh is a promising network topology and is suitable for a range of network-based computing systems. Although there are few models reported for hypermeshes with uniform traffic pattern, no analytical model has been reported to deal with hot-spot traffic. Since many parallel applications exhibit non-uniform traffic patterns such as hot-spots, uniform traffic assumption is not always justifiable in practice. In this study, we propose a new analytical model to predict the mean message latency in wormhole-switched hypermeshes in the presence of hot-spot traffic. The proposed model can also calculate the mean latency under uniform traffic load when the hot-spot ratio is set to zero.... 

In this paper, we propose and analyze flocking algorithms in a network of second-order agents with bounded control inputs and nonlinear intrinsic dynamics. We consider a general switching network topology, for velocity information exchange, rather than undirected or fixed directed network topology with a directed spanning tree. The proposed adaptive controller architecture applies a leader-following strategy in which the pinning scheme is defined based on the interaction topology. Finally, some examples are presented to illustrate the theoretical results  

In this paper, after studying the demands and requirements of a perfect smart grid and specifications of network topology and sensor nodes utilized in a Wireless Sensor Network [WSN], a manipulated version of them is proposed to be combined with smart grid in order to improve the data acquisition step, increase the security and facilitate the process of information and desired commands from users. We will take the advantage of computer simulations to illustrate improved capacity and speed of this method. Finally, we will analyze the advantages of employing this proposed structure in a smart grid  

In this work, the modified Flory-Huggins coupled with the free-volume concept and the artificial neural network models were used to obtain the osmotic pressure of aqueous poly(ethylene glycol) solutions. In the artificial neural network, the osmotic pressure of aqueous poly(ethylene glycol) solutions depends on temperature, molecular weight and the mole fractions of poly(ethylene glycol) in aqueous solution. The network topology is optimized and the (3-1-1) architecture is found using optimization of an objective function with batch back propagation (BBP) method for 134 experimental data points. The results obtained from the neural network in obtaining of the osmotic pressure of aqueous... 

Hypermesh is a promising network topology and is suitable for a range of network-based computing systems. Although there are few models reported for hypermeshes with uniform traffic pattern, no analytical model has been reported to deal with hot-spot traffic. Since many parallel applications exhibit non-uniform traffic patterns such as hot-spots, uniform traffic assumption is not always justifiable in practice. In this study, we propose a new analytical model to predict the mean message latency in wormhole-switched hypermeshes in the presence of hot-spot traffic. The proposed model can also calculate the mean latency under uniform traffic load when the hot-spot ratio is set to zero.... 

Peer-to-Peer overlay networks are an attractive foundation for video streaming. However, live Peer-to-Peer media streaming systems face many challenges such as bandwidth heterogeneity, node churn, and selfish nodes. Although many tree based and mesh based streaming protocols have been proposed, each has its own drawbacks such as unreliability and unfairness in tree based and long startup delay and complex scheduling in mesh based protocols. In this paper, we propose a new video streaming protocol called LayeredCast main features of which are: 1) Hybrid: Drawbacks of the simple approaches are compensated using a hybrid of mesh and tree overlays. 2) Layered Video: Provides an adaptive scheme... 

In this paper, we consider multiple cache-enabled clients connected to multiple servers through an intermediate network. We design several topology-aware coding strategies for such networks. Based on the topology richness of the intermediate network, and types of coding operations at internal nodes, we define three classes of networks, namely, dedicated, flexible, and linear networks. For each class, we propose an achievable coding scheme, analyze its coding delay, and also compare it with an information theoretic lower bound. For flexible networks, we show that our scheme is order-optimal in terms of coding delay and, interestingly, the optimal memory-delay curve is achieved in certain... 

Optimal transmission switching (OTS) along with optimal bus-bar switching, also known as network topology optimization (NTO), has been previously proposed and utilized as a powerful tool to reduce operational costs. However, operational constraints and reliability considerations of NTO problem have not been addressed properly. In this paper, operational constraints are integrated in NTO problem and the effect of transmission network switching on expected interruption cost (EIC) is investigated. Moreover, a novel approach based on pool of solutions approach is presented, which can generate various switching scenarios. In doing so, the decision maker would be able to analyze and choose the... 

One of the major problems in liberalized power markets is loss allocation. In this paper, a new method for allocating transmission losses to pool market participants is proposed. The proposed method is fundamentally based on Bialek's "Tracing the flow of electricity" method. The losses is allocated to market participants using the loss weight factors (LWFs) which are obtained from the square current magnitude and Z-bus matrix. The LWF method is based on a solved load flow and strongly emphasizes on current magnitude while considers network topology. The method has been implemented and tested on several networks and one sample summarized in the paper. The results show that the method has an... 

Stretched hypercube has recently been introduced as an attractive alternative to the well-known hypercube. Previous research on this network topology has mainly focused on topological properties and VLSI aspects of this network In this paper, we propose some deterministic and adaptive routing algorithms for the stretched hypercubes. The performance of stretched hypercubes using the proposed routing algorithms is then evaluated by means of simulation experiments. Experiments are reahzed under different working loads and for different network actors. © 2008 IEEE  

Mobile Ad-hoc Networks are networks that have a dynamic topology without any fixed infrastructure. To transmit information in ad-hoc networks, we need robust protocols that can cope with constant changes in the network topology. The known routing protocols for mobile ad-hoc networks can be classified in two major categories: proactive routing protocols and reactive routing protocols. Proactive routing protocols keep the routes up-to-date to reduce delay in real-time applications but they have high control overhead. The control overhead in reactive routing protocols is much less than proactive routing protocols; however, the routes are discovered on demand, which is not suitable for real-time...