Sharif Digital Repository

Analytical modelling is indeed the most cost-effective method to evaluate the performance of a system. Several analytical models have been proposed in the literature for different interconnection network systems. This paper proposes an accurate analytical model to predict message latency in wormhole-switched star graphs with fully adaptive routing. Although the focus of this research is on the star graph but the approach used for modelling can be, however, used for modelling some other regular and irregular interconnection networks. The results obtained from simulation experiments confirm that the proposed model exhibits a good accuracy for various network sizes and under different operating... 

Many theoretical-based comparison studies, relying on graph structural and algorithmic properties, have been conducted for the hypercube and the star graph. None of these studies, however, have considered real working conditions and implementation limits. We have compared the performance of the star and hypercube networks for different message lengths and number of virtual channels, and considered two implementation constraints, namely the constant bisection bandwidth and constant node pin-out. We use two accurate analytical models, already proposed for the star graph and hypercube, and implement the parameter changes imposed by technological implementation constraints. When no constraint is... 

Performance evaluation is an important engineering tool that provides valuable feedback on design choices in the implementation of multi-core systems such as parallel systems, multicomputers, and Systems-on-Chip (SoCs). The significant advantage of analytical models over simulation is that they can be used to obtain performance results for large systems under different configurations and working conditions which may not be feasible to study using simulation on conventional computers due to the excessive computation demands. We present Caspian, a novel analytic performance model, aimed to minimize prediction cost, while providing prediction accuracy. This is accomplished by using a G/G/1... 

Future System-on-Chip (SoC) designs will need efficient on-chip communication architectures that can provide efficient and scalable data transport among the Intellectual Properties (IPs). Designing and optimizing SoCs is an increasingly difficult task due to the size and complexity of the SoC design space, high cost of detailed simulation, and several constraints that the design must satisfy. For efficient design of SoCs, an efficient mapping of IPs onto Networks-on-Chip (NoCs) is highly desirable. Towards this end, we have presented PERMAP, a PERformance-aware MAPping algorithm which maps the IPs onto a generic NoC architecture such that the average communication delay is minimized. This is... 

The star graph was introduced as an attractive alternative to the well-known hypercube and its properties have been well studied in the past. Most of these studies have focused on topological properties and algorithmic aspects of this network. Although several analytical models have been proposed in the literature for different interconnection networks, none of them have dealt with star graphs. This paper proposes the first analytical model to predict message latency in wormhole-switched star interconnection networks with fully adaptive routing. The analysis focuses on a fully adaptive routing algorithm which has shown to be the most effective for star graphs. The results obtained from... 

The star graph was introduced as an attractive alternative to the well-known hypercube and its properties have been well studied in the past. Most of these studies have focused on topological properties and algorithmic aspects of this network. In this paper, the performance of nine fully-adaptive routing algorithms in the star network are studied under uniform (with and without locality) and hotspot traffic patterns. The performance factors considered are the average message latency and network utilization. We consider three basic routing algorithms (two hop scheme routing algorithms: positive-hop and negative-hop, and Msic's routing algorithm) and two other improved sets of improved... 

In this paper, we examine the effect of physics-based input data in artificial neural network (ANN) for indoor propagation. Our prior knowledge of electromagnetic propagation forms, enables us to predict path loss for a specified geometry. There is a good agreement between ANN predicted output and ray-tracing results for a simple room and the error reduces notably compared to related works. Additionally, we explore feature extraction for more complex scenarios. © 2023 IEEE  

Modern SoC architectures use NoCs for high-speed inter-IP communication. For NoC architectures, high-performance efficient routing algorithms with low power consumption are essential for real-time applications. NoCs with mesh and torus interconnection topologies are now popular due to their simple structures. A torus NoC is very similar to the mesh NoC, but has rather smaller diameter. For a routing algorithm to be deadlock-free in a torus, at least two virtual channels per physical channel must be used to avoid cyclic channel dependencies due to the warp-around links; however, in a mesh network deadlock freedom can be insured using only one virtual channel. The employed number of virtual... 

Modern SoC architectures use NoCs for high-speed inter-IP communication. For NoC architectures, high-performance efficient routing algorithms with low power consumption are essential for real-time applications. NoCs with mesh and torus interconnection topologies are now popular due to their simple structures. A torus NoC is very similar to the mesh NoC, but has rather smaller diameter. For a routing algorithm to be deadlock-free in a torus, at least two virtual channels per physical channel must be used to avoid cyclic channel dependencies due to the warp-around links; however, in a mesh network deadlock freedom can be insured using only one virtual channel. The employed number of virtual... 

Network-on-Chip (NoC) has been proposed as a solution for addressing the design challenges of future high-performance nanoscale architectures. Thus, it is of crucial importance for a designer to ha ve access to fast methods for evaluating the performance of on-chip networks. To this end, we present a Markovian model for evaluating the latency and energy consumption of on-chip networks. We compute the a verage delay due to path contention, virtual channel and crossbar switch arbitration using a queuing-based approach, which can capture the blocking phenomena of wormhole switching quite accurately. The model is then used to estimate the power consumption of all routers in NoCs. The performance... 

Multivariate ring-model description and the delay operator are used to represent LTI systems with delays in the states, inputs and outputs. By using the concept of μ-Decentralized Fixed Mode (μ-DFM) and generalized Nyquist criterion, it is demonstrated that the steady-state gain information yet remains the only information necessary to assess integral stabilizability (IS), integral controllability (IC), integral controllability with integrity (ICI) and decentralized integral controllability (DIC) of LTI time-delay systems. The conditions involve no approximation of the delay terms. Furthermore, it is demonstrated that a previous assumption on the existence of a stabilizing and stable... 

Three novel methods, named α, ζ and ϵ, are suggested in this paper to recover the performance loss during switching in the gas turbine control systems. The Minimum Command Selection (MCS) in the gas turbine control systems prompts this performance loss. Any step towards more productivity with less aging factors have a great impact on the gas turbine's lifetime profit and vice versa. Although many hardware upgrades have been studied and applied to accomplish this, in many cases a low-risk manipulation in the software may yield equivalent achievement. State of the art gas turbine control systems are supposed to handle various forms of disturbances, several operation modes and relatively high... 

Three novel methods, named α, ζ and ϵ, are suggested in this paper to recover the performance loss during switching in the gas turbine control systems. The Minimum Command Selection (MCS) in the gas turbine control systems prompts this performance loss. Any step towards more productivity with less aging factors have a great impact on the gas turbine's lifetime profit and vice versa. Although many hardware upgrades have been studied and applied to accomplish this, in many cases a low-risk manipulation in the software may yield equivalent achievement. State of the art gas turbine control systems are supposed to handle various forms of disturbances, several operation modes and relatively high... 

The increasing capabilities of control systems, driven by abundant data and computational resources, necessitate the incorporation of data-based techniques with model-based approaches. While mathematical models exist for air and space vehicles, they may not fully meet the requirements for expanding control system capabilities. Consequently, the development of data-based extensions in collaboration with these models becomes crucial to provide specific analysis and synthesis tools in the hybrid realm for practical cases. This article introduces the data-assisted control (DAC) framework for aerospace vehicles, with the NASA generic transport model serving as the platform for study. By... 

Many theoretical-based comparison studies, relying on the graph theoretical viewpoints with using structural and algorithmic properties, have been conducted for the hypercube and the star graph. None of these studies, however, considered real working conditions and implementation limits. We have compared the performance of the star and hypercube networks for different message length and virtual channels and considered two implementation constraints, namely the constant bisection bandwidth and constant node pin-out. We use two accurate analytical models already proposed for the star graph and hypercube and implement the parameter changes imposed by technological implementation constraints.... 

A new method for production of bimetallic rods, utilizing the equal channel angular extrusion (ECAE) process has been introduced before by previous researchers, but no attempt has been made to assess the effect of different temperatures and holding times in order to achieve a diffusional bond between the mating surfaces. In present research copper sheathed aluminum rods have been ECAEed at room temperature and subsequently held at a constant ECAE pressure, at different temperatures and holding times to produce a diffusional bond between the copper sheath and the aluminum core. The bonding quality of the joints was examined by shear strength test and a sound bonding interface was achieved.... 

Energy storage is one of the most important components of renewable energy systems. Among different methods, thermal energy storage (TES) in forms of sensible or latent has been the subject of many studies in the past decades. The main difficulty in optimal design of storage tanks is associated with low thermal conductivity of the storing (solid or phase change) material. In fact, the distribution of thermal energy from a source to the body of storing material poses a volume to point problem which is the subject of constructal theory. Therefore, the objective of the present paper is to investigate the transient behavior of a rectangular thermal energy storage tank equipped with fin... 

A family of conformational rheological models for multi-component miscible polymer blends is developed using a modified form of the Poisson bracket formulation. Two conformation tensors called c1 and c2 are introduced to show the orientation of the first and the second components of a blend, respectively. The mobility tensor and the energy function for each blend component are expressed in terms of these conformation tensors. The interaction effects are also included by energy expressions. The predictions of this family of "volume-preserving" models are illustrated for a Hookean-type energy function and several expressions of the modified mobility tensors. The results are illustrated for... 

It has been realized that the raft (mat) foundations are capable of bearing very large loads when they are assisted with a pile group. The contribution of both raft and piles to carry the surcharge loads is taken into account, considering the stiffness and strength of involved elements in the system, i.e. piles, raft and surrounding soil. The piles are usually required not to ensure the overall stability of the foundation but to act as settlement reducers. There is an alternative design in which, the piles are nonconnected from the raft to reduce the settlement, which are then known to be "settlement reducer non-connected piles" to increase the system stiffness. In this paper, two and three... 

In this paper, an effort has been made to model the 60 GHz wireless channel using a precise yet fast and simple method for short outdoor links that are a possible area for the use of 60 GHz wireless connectivity for high data rate services with dense frequency reuse. Considering the certain properties of this frequency band, it is possible to obtain a simple channel model to replace time consuming ray tracing methods with simpler models by disregarding low power multipath components. The street canyon model has been considered here as a replacement for ray tracing in an urban environment with below rooftop antennas to predict received power along streets and the results have been compared to...