Sharif Digital Repository

As a result of the emerging use of mesh-based multicomputers (and recently mesh-based multiprocessor systems-on-chip), issues related to processor management have attracted much attention. In a mesh-based multiprocessor, after repeated submesh allocations and de-allocations, the system network may be fragmented, i.e. there might be unallocated nodes in the network. As a result, in a system with contiguous processor allocation, no new tasks can start running due to the lack of enough free adjacent processors to form a suitable submesh. Although there might be enough free processors available, they remain idle until the allocator can find a set of adjacent free nodes forming a submesh to be... 

A finite element solution procedure is presented for the simulation of transient incompressible fluid flows using triangular meshes. The algorithm is based on the artificial compressibility technique in connection with a dual time-stepping approach. A second-order discretization is employed to achieve the required accuracy in real-time while an explicit multistage Runge-Kutta scheme is used to march in the pseudo-time domain. A standard Galerkin finite element method, stabilized by using an artificial dissipation technique, is used for the spatial discretization. The performance of the proposed algorithm is demonstrated by solving a set of internal and external problems including flows with... 

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,... 

In this paper, a new topology for multicomputer interconnection networks, based on triangular mesh, is proposed. The new network, referred to as the triangular pyramid (or tripy for short), has L levels of triangular mesh. We study some basic important properties of the proposed network as well as introduce a routing algorithm for the tripy network based on the routing of triangular meshes. We prove that this form of pyramidal network is Hamiltonian, Hamiltonian-connected, and pancyclic. We also prove that the proposed network is 6-colorable and conduct a brief comparison of the tripy and its traditional pyramid counterpart. Our results show that the proposed network has higher scalability,... 

Analytical models exist for evaluating gossip-based information propagation. Up to now these models were developed only for fully connected networks. We provide analytical models for information propagation of a push-pull gossiping protocol in a wireless mesh network. The underlying topology is abstracted away by assuming that the wireless nodes are uniformly deployed. We compare our models with simulation results for different topologies  

Mesh-based interconnection networks are the most popular inter-processor communication infrastructures used in current parallel supercomputers. Although many analytical models of n-D torus interconnection networks have been reported in the literature over the last decade, few analytical models have been proposed for the 2-D mesh case (and not for the general n-D mesh network) using inaccurate approximations as they have not fully incorporated the asymmetry effects of the mesh topology, in order to reduce the model complexity. There has not been reported, to the best of our knowledge, a performance model that can deal with the n-D mesh network. To fill this gap, in this paper, we propose the... 

In this paper, a new topology for multicomputer interconnection networks, based on triangular mesh, is proposed. The new network, referred to as the triangular pyramid (or tripy for short), has L levels of triangular mesh. We study some basic important properties of the proposed network as well as introduce a routing algorithm for the tripy network based on the routing of triangular meshes. We prove that this form of pyramidal network is Hamiltonian, Hamiltonian-connected, and pancyclic. We also prove that the proposed network is 6-colorable and conduct a brief comparison of the tripy and its traditional pyramid counterpart. Our results show that the proposed network has higher scalability,... 

In this study, the effects of the mesh barrier on the free dispersion of ammonia were numerically investigated under different atmospheric conditions. This study presents the detail and flow feature of the dispersion of ammonia through the mesh barrier on various free stream conditions to decline and limit the toxic danger of the ammonia. It is assumed that the dispersion of the ammonia occurred through the leakage in the pipeline. Parametric studies were conducted on the performance of the mesh barrier by using the Reynolds-averaged Navier-Stokes equations with realizable κ-ε turbulence model. Numerical simulations of ammonia dispersion in the presence of mesh barrier revealed significant... 

Mesh-reinforced cellulose acetate (CA)-based membranes were prepared for forward osmosis (FO) by immersion precipitation. Casting compositions such as CA percent and 1, 4-dioxane/acetone ratio and also preparation conditions such as evaporation time, coagulation bath and annealing temperatures were tested for membranes’ performance. The results were compared with commercially CTA membranes. The best membrane (17.9% polymer and 1, 4-dioxane/acetone ratio of 1.89) showed water flux of 9.3 L/m2h (LMH) and RSF of 0.536 mol NaCl/m2h. Moreover, the membrane structure was reinforced by a polyester mesh, which created micro pores in the back of the membrane. This caused higher water flux and RSF... 

In this paper, we propose a solution for the problem of capturing an intruder in two popular interconnection topologies namely, the mesh and the torus. A set of agents collaborate to capture a hostile intruder in the network. While the agents can move in the network one hop at a time, the intruder is assumed to be arbitrarily fast i.e. it can traverse any number of nodes contiguously as far as there are no agents in those nodes. Here we consider a new version of the problem where each agent can replicate new agents when needed, i.e. the algorithm starts with a single agent and new agents are created on demand. We define a new class of algorithms for capturing an intruder. In particular, we... 

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 2D hypersonic real gas flow has been analyzed on an adaptive unstructured grid using Roe's Flux Difference Splitting and AUSM schemes. In high temperature and hypersonic regime, the flow is extremely compressible and ideal gas assumption is not valid. In fact in these flows, due to changes in the flow properties, composition of fluid elements will also change. To solve steady and unsteady 2D Euler' equations for real gases, assumption of a general equation of state for real gases in equilibrium is considered. We use an unstructured Delaunay triangulation and adapt it in high gradient areas. Results are compared with known numerical and exact solutions. The scheme is convergent, and... 

In optoelectronic OTIS multicomputer networks (also known as Swapped networks), electrical and optical interconnects are used for local and global communication, respectively. An interesting instance of the OTIS multicomputers is the OTIS-mesh. Pancyclicity is of great importance in the implementation of a variety of parallel algorithms in multicomputers. This paper addresses the Pancyclicity problem of OTIS-mesh. More precisely, we prove that if the factor graph G of an OTIS network is a 2-D or 3-D mesh with at least one even radix, OTIS-G can embed any cycle of length l, l?{4,6,7,8,9,...,|G|2}  

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,... 

In optoelectronic OTIS multicomputer networks (also known as Swapped networks), electrical and optical interconnects are used for local and global communication, respectively. An interesting instance of the OTIS multicomputers is the OTIS-mesh. Pancyclicity is of great importance in the implementation of a variety of parallel algorithms in multicomputers. This paper addresses the Pancyclicity problem of OTIS-mesh. More precisely, we prove that if the factor graph G of an OTIS network is a 2-D or 3-D mesh with at least one even radix, OTIS-G can embed any cycle of length l, l∈{4,6,7,8,9,...,|G|2}  

Because of their exclusive features, millimeter wave directive mesh networks can be considered for small cell backhaul support in urban environments. For this purpose, a network of closely spaced stations has been considered with very directive line-of-sight links operating in the 60-GHz band. An attempt is made to evaluate channel response and interference behavior in such a network, taking into account the effect of building blockage. A simple grid of building blocks is considered as the propagation environment, and wave propagation is simulated using 2.5-dimensional (2.5D) ray tracing (2D with ground effect) to calculate the received signal at different nodes in the network. The results... 

Nowadays, deployment of peer-to-peer video streaming systems over wireless mesh networks has attained raising popularity among large number of users around the world. In this paper, we present an efficient peer-to-peer live video streaming architecture over multi-hop wireless mesh networks. In our proposed architecture, we take the physical topology of network into account and based on a distributed distributed locality-aware neighbor selection algorithm in the overlay construction phase, we generate an efficient mesh-based overlay on top of wireless mesh networks. In locality-aware neighbor selection algorithm, instead of choosing randomly, peers find their best neighbors based on their...