Sharif Digital Repository

The characteristics of correlated networks, generated from uncorrelated networks, were studied. New correlated networks with a considerable clustering were obtained from the line graphs of uncorrelated network. The transformation by which random graphs were converted to their line (edge-dual) graphs was explained. The solution for site percolation on the transformed graphs was also studied  

In this paper, we study the performance of optical code-division multiple access (CDMA) systems using various receivers structures. Two general classes of receivers based on required electronic bandwidth are studied. Optical orthogonal codes (OOCs) are utilized as signature sequences and the performance studied in this paper takes into account the effect of all major noise sources, i.e., quantum shot-noise, dark current noise, and Gaussian circuit noise. Furthermore, this paper introduces a generalized method of analyzing the performance of various optical CDMA receiver structures. Required mean number of photon count per chip time for reliable transmission of data bits for various receiver... 

In this study, we consider a capacitated location–multi-allocation–routing problem with population-dependent random travel times. The objective is to find appropriate locations as server locations among the candidate locations, allocate the existing population in each demand node to server locations, and determine the movement path of each member to reach its corresponding server with respect to the simultaneous change of the random travel times so that the expected total transportation time is minimized. In our study, the concept of population-dependent random travel times incurs two issues: (1) consideration of some random factors in computing the travel times and (2) impact of the... 

a small array of Water Cherenkov Detectors (WCDs) has recorded 600000 events related to extensive air showers in Tehran during one year at an altitude of 1200m. By employing the method of obtaining count in each time interval distributions we obtained the distribution of extensive air showers. 17 events were found in our data set which are more probable to be related to primary gamma ray photons. For more certainty we did a simulation to compare acquired results from simulation and data to become sure if 17 extensive air showers are electromagnetic or not  

At ALBORZ Observatory in Tehran (51° 200 , 35 ° 430' , 1200 m) we accumulated a complete year of data by a 4-fold square array of Water Cherenkov Detectors (WCDs) with the side 6.08 m. It is recorded about 800,000 fine EAS events from 2006/11/12 to 2007/11/20 by the approximate recording rate of 0.03. Time differences between each two, three, four, five and ... have a very good agreement with gammafunction, which shows the correct random nature of the events. Of course we expect that about less than 1% of the EAS events (≤9000 events) be electromagnetic and naturally not random, but the contribution is so small. Then by Farley/Storey procedure [1] we found a signature of real sidereal data.... 

In high-yields process monitoring, the Geometric distribution is particularly useful to control the cumulative counts of conforming (CCC) items. However, in some instances the number of defects on a nonconforming observation is also of important application and must be monitored. For the latter case, the use of the generalized Poisson distribution and hence simultaneously implementation of two control charts (CCC & C charts) is recommended in the literature. In this paper, we propose an artificial neural network approach to monitor high-yields processes in which not only the cumulative counts of conforming items but also the number of defects on nonconforming items is monitored. In order to... 

The inventory system under consideration consists of one central warehouse and many identical retailers controlled by continuous review inventory policy ( R, Q). We assume independent Poisson demands with constant transportation times for the retailers and a constant lead time for replenishing orders from an external supplier for the warehouse. Unsatisfied demands are assumed to be lost in the retailers and unsatisfied retailer orders are backordered in the warehouse. We develop an approximate cost function to find optimal reorder points for given batch sizes in all installations and the related accuracy is assessed through simulation. © 2005 Elsevier B.V. All rights reserved  

In this paper, we develop a multi-objective model to optimally control the lead time of a multistage assembly system, using an interactive method. The multistage assembly system is modelled as an open queueing network, whose service stations represent manufacturing or assembly operations. It is assumed that the product order arrives according to a Poisson process. In each service station, there is either one or infinite number of servers (machines) with exponentially distributed processing time, in which the service rate (capacity) is controllable. The transport times between the service stations are independent random variables with generalized Erlang distributions. The problem is... 

We study queueing systems where customers have strict deadlines until the end of their service. An analytic method is given for the analysis of a class of such queues, namely, M(n)/M/1 + G models with ordered service. These are single-server queues with state-dependent Poisson arrival process, exponential service times, FCFS service discipline, and general customer impatience. We derive a closed-form solution for the conditional probability density function of the offered sojourn time, given the number of customers in the system. This is a novel result that has not been seen before. Using this result, we show how the probability measure induced by the offered sojourn time is computed, and... 

This paper introduces a stochastic dynamic power management policy for soft real-time systems which uses DVS to consume less power in the main processor while satisfying the performance constraints. The idea is based on a Markovian model of the system. The system under study is a single. processor system with real-time jobs which arrive according to a Poisson process and have exponentially distributed deadlines and service times. Since the speed levels in real processors are not continuous, the required service rate for a given performance is estimated in a probabilistic manner using its two immediate neighboring speeds. Experimental results show that the long run power consumption of the... 

In this letter, a new molecular modulation scheme for nanonetworks is proposed. To evaluate the scheme, a system model based on the Poisson distribution is introduced. The error probability of the proposed scheme as well as that of two previously known schemes, the concentration and molecular shift keying modulations, are derived for the Poisson model by taking into account the error propagation effect of previously decoded symbols. The proposed scheme is shown to outperform the previously introduced schemes. This is due to the fact that the decoding of the current symbol in the proposed scheme does not encounter propagation of error, as the decoding of the current symbol does not depend on... 

Wireless Ad-hoc Networks have been proposed for variety of applications. In this paper our goal is to find crisis points in the roads, such as accident locations, and asphalt-destruction points, which may cause traffics along the roads. The applied method for traffic prediction is based on back propagation algorithm. In this paper the length of packets are assumed to be constant. Along the road the traffic is modeled by a Poisson Process. With this model we can produce packets. The number of packets which are sending from a typical node to the other nodes is controlled by a fuzzy system. By appropriate training of a neural network, we have shown that, having the traffic packets at time (t)... 

In recent years, Wireless Ad-hoc networks have been considered as one of the most important technologies. The application domains of Wireless Ad-hoc Networks gain more and more importance in many areas. One of them is controlling and management the packet traffic. In this paper our goal is controlling the performance of every sections of pipeline of the factory by checking network periodically. Along the factory the traffic is modeled with a Poisson process. We present, with obtaining traffic packets at time (t) for each node in Wireless Ad-hoc Network, we can completely train a Neural Network and successfully predict the traffic at time (t+1) for each node. By this way we can recognize the... 

In this paper we investigate the Shannon capacity of single and parallel Poisson channels in different scenarios. At first, by examining the capacity equation of the single Poisson channel, the minimum average power that maximizes the capacity is found. Then, applying the method of Lagrange multipliers on the capacity expression of the parallel Poisson channel, we obtain the optimum power allocation maximizing the parallel Poisson channel capacity  

This paper is devoted to the study of some asymptotic behaviors of Poisson-Voronoi tessellation in the Euclidean space as the space dimension tends to ∞. We consider a family of homogeneous Poisson-Voronoi tessellations with constant intensity λ in Euclidean spaces of dimensions n = 1, 2, 3,... First we use the Blaschke-Pètkantschin formula to prove that the variance of the volume of the typical cell tends to 0 exponentially in dimension. It is also shown that the volume of intersection of the typical cell with the co-centered ball of volume u converges in distribution to the constant λ-1 (1-e-λu). Next we consider the linear contact distribution function of the Poisson-Voronoi tessellation... 

In this paper, we study the effect of non-Poisson traffic patterns on energy consumption for IEEE 802.16e nodes while operating in the sleep mode. In the sleep mode, a Mobile Subscribe Station (MSS) sleeps for a sleep interval and wakes up at the end of this interval in order to check buffered packet(s) at Base Station (BS) destined to it. If there is no packet, the MSS increases the sleep window up to the maximum value and sleeps again. For a more general traffic pattern (rather than Poisson), we evaluate the average power consumption. Based on our analysis, we conclude that traffic pattern plays an important role in power consumption. ©2007 IEEE  

This paper considers a single-item, two-echelon, continuous-review inventory model. A number of retailers have their stock replenished from a central warehouse. The warehouse in turn replenishes stock from an external supplier. The demand processes on the retailers are independent Poisson. Demand not met at a retailer is lost. The order quantity from each retailer on the warehouse and from the warehouse on the supplier takes the same fixed value Q, an exogenous variable determined by packaging and handling constraints. Retailer i follows a (Q, Ri) control policy. The warehouse operates an (SQ, (S - 1)Q) policy, with non-negative integer S. If the warehouse is in stock then the lead time for... 

End-to-end delay, throughput, energy consumption, and silicon area are the most important design metrics of networks-on-chip (NoCs). Although several analytical models have been previously proposed for predicting such metrics in NoCs, very few of them consider the effect of message waiting time in the buffers of network routers for predicting overall power consumptions and none of them consider structural heterogeneity of network routers. This paper introduces two inter-related analytical models to compute message latency and power consumption of NoCs with arbitrary topology, buffering structure, and routing algorithm. Buffer allocation scheme defines the buffering space for each individual...