Sharif Digital Repository

The reliability of wireless sensor networks (WSNs) depends on both sensing coverage and reliable transmission of collected data provided by the target cluster of sensors in the proximity of the phenomenon to the observer. In this paper, we establish a probabilistic fundamental quantitative notion for performance-critical applications on reliable information transfer and propose a new analytical model to calculate the coverage-oriented reliability of cluster-based WSNs. Here, the packet loss probability is modeled as a function of two main parameters. The first is the probability of link failure when the node's buffer at the end point of the link is full (discarding the packet) or when the... 

It is known that the thermomechanical processing is one of the most important techniques for improving quality and mechanical properties of microalloyed steels. In this paper, the main parameters of hot forging (preheat temperature, strain and post-forging cooling rate) on the primary austenite grain size of vanadium microalloyed steel (30MSV6) were studied. From this investigation, it was found that increasing preheat temperature from 1150 °C to 1300 °C will result in a decrease in grain size number. Furthermore, it has shown that as the strain increases, the austenite grain size number increases, as is evident for the two cooling rates of 2.5 °C/s and 1.5 °C/s for primary austenite.... 

Rate, energy and delay are three main parameters of interest in ad-hoc networks. In this paper, we discuss the problem of maximizing network utility and minimizing energy consumption while satisfying a given transmission delay constraint for each packet. We formulate this problem in the standard convex optimization form and subsequently discuss the tradeoff between utility, energy and delay in such framework. Also, in order to adapt for the distributed nature of the network, a distributed algorithm where nodes decide on choosing transmission rates and probabilities based on their local information is introduced. ©2009 IEEE  

In this article, numerical simulations are performed to investigate the performance of the thermal diffusion column for the separation of n-heptane/benzene mixture. The present work tried to optimize column by analyzing significant parameters such as feed flow rate, temperature and cut. In order to obtain the hydrodynamic and temperature and mass distribution inside thermal diffusion column, computational fluid dynamic (CFD) method is applied to solve the Navier–Stocks equations. Numerical simulations are conducted to study the main parameters in both stationary and time-dependent conditions. By using the separation work unit as a function of cut, the optimal cut for maximum SWU occurs... 

The permeability of roller-compacted concrete (RCC) substantially affects its functionality and safety. This study investigates the effect of mix design parameters on the performance of RCC. For this purpose, approximately 500 laboratory specimens were prepared and tested. A formula and an artificial neural network (ANN) were proposed to predict the permeability coefficient of RCC by considering the main parameters, which were then verified independently using new specimens. Furthermore, the experimental data were analyzed by the Taguchi method and analysis of variance (ANOVA) to evaluate the level of parameter contribution. Based on the results, the permeability coefficient was highly... 

This study investigates the mechanical properties of lightweight polymer concrete (LWPC) containing four different polymer ratios (10%, 12%, 14%, and 16%) tested at three different temperatures (−15 °C, +5 °C, and +25 °C) using destructive and non-destructive tests. In addition, a series of expressions are suggested to predict the splitting-tensile, flexural and impact strength of LWPC based on the main parameters and compressive strength. The analysis of variance (ANOVA) method was also used to determine relative contributions of the experimental parameters. The results of the destructive tests show that increasing the polymer ratio caused an increase in the compressive, splitting-tensile,... 

In this research, the main parameters of the multivariate cumulative sum (CUSUM) control chart (the reference value k, the control limit H, the sample size n and the sampling interval h) are determined by minimising the Lorenzen-Vance cost function [Lorenzen, T.J., and Vance, L.C. (1986), The Economic Design of Control Charts: A Unified Approach, Technometrics, 28, 3-10], in which the external costs of employing the chart are added. In addition, the model is statistically constrained to achieve desired in-control and out-of-control average run lengths. The Taguchi loss approach is used to model the problem and a genetic algorithm, for which its main parameters are tuned using the response... 

The main purpose of this paper is modeling and simulation of in-situ releasing of smart nano-sized core-shell particles at the water-oil interface during polymer flooding. During the polymer flooding process, when these nano-particles reach the water-oil interface, migrate to the oil phase and the hydrophobic layer of them dissolves in this phase. After dissolution of this protective nano-sized layer, the hydrophilic core containing a water-soluble ultra high molecular weight polymer diffuses back into the water phase and with dissolving in this phase, dramatically increases viscosity of flooding water in the neighborhood of the water-oil interface. In this study, two different... 

In nonlinear static (pushover) methods of analysis as an alternative to time history analysis, the capacity curve of the structure is established with respect to the roof displacement. Disproportionate increases in the roof displacement and even outright reversals of the higher modes can distort the capacity curve of the equivalent single degree of freedom system in these kinds of method, including MPA. To overcome this problem, recently, "Energy-Based" the Modal Pushover Analysis (Energy-Based MPA) method has been introduced. In this method, the absorbed energy and/or the external work in the pushover analysis is considered. Accordingly, the assessment of the Energy-Based MPA method is... 

In this paper, the performance of a turbocharger twin-entry radial inflow turbine is investigated analytically and experimentally under steady state, full and partial admission conditions. In this modeling, the mass flow rate, pressure ratio and efficiency of the turbine are assumed unknown. The turbine geometry and the inlet total pressure and temperature are known, hence, the turbine performance characteristics can be obtained. In the turbocharger laboratory, performance characteristics of the turbine are determined, measuring the main parameters for various operating conditions. Comparing the model and experimental results shows good agreement. Also, considering the effect of test...