AMIRKABIR INTERNATIONAL JOURNAL OF MODELING, IDENTIFICATION, SIMULATION AND CONTROL
Year:2012 | Volume:44 | Issue:1|Papers Count:7

This paper considers an important model of boundary value problem with a condition at infinity namely combined free and forced convection over a plane of arbitrary shape embedded in a fluid-saturated porous medium, this model admits dual solutions, and uses a technique, which is to some extent modification of homotopy analysis method (HAM), in order to obtain dual solutions analytically with high accuracy.

Wireless Multimedia Sensor Networks (WMSNs) undergo congestion when a link (or a node) becomes overpopulated in terms of incoming packets. In WMSNs this happens especially in upstream nodes where all incoming packets meet and directed to the sink node. Congestion in networks, if not handled properly, might lead to congestion collapse which deteriorates the quality of service (QoS). Therefore, in order to avoid such situations corresponding actions should be taken into account so that to yield lower packet loss and consequently energy loss that is of utmost importance in WSNs. However, the term "packet loss" as implied by today's literature might not be effective in many applications especially in multimedia sensor networks. In this paper a new weighted packet loss metric is proposed which is best suited for multimedia sensor networks that convey packets of different priority classes. The proposed method then tries to minimize the aforementioned criterion by means of fuzzy queue management and a newly introduced adaptive rate control mechanism, in the presence of both abrupt and gradual changes in network dynamics. The employment of these two techniques provides us a synergy to handling short term and long term variations arising through the underlying simulated networks. The simulation results approve the superiority of the proposed approach over the selected competitive method when dealing with packets of different priorities.

In order to better understand the mechanical properties of biological cells, characterization and investigation of their material behavior is necessary. In this paper hyperelastic Neo-Hookean material is used to characterize the mechanical properties of mouse oocyte cell. It has been assumed that the cell behaves as continuous, isotropic, nonlinear and homogenous material for modeling. Then, by matching the experimental data with finite element (FE) simulation result and using the Levenberg–Marquardt optimization algorithm, the nonlinear hyperelastic model parameters have been extracted. Experimental data of mouse oocyte captured from literatures. Advantage of the developed model is that it can be used to calculate accurate reaction force on surgical instrument or it can be used to compute deformation or force in virtual reality based medical simulations.

This paper assumes each user has more than one queue, derives a new packet-dependant proportional fairness power allocation pattern based on the sum of weight capacity and the packet's priority in users' queues, and proposes 4 new cross-layer packet-dependant OFDM scheduling schemes based on proportional fairness for heterogeneous classes of traffic. Scenario 1, scenario 2 and scenario 3 lead respectively artificial fish swarm algorithm, self-adaptive particle swarm optimization algorithm and cloud adaptive particle swarm optimization algorithm into sub-carrier allocation in packet-dependant proportional fairness scheduling, and use respectively new power allocation pattern, self-adaptive particle swarm optimization algorithm and population migration algorithm to allocate power. Scenario 4 uses greedy algorithm concerning fairness to allocate sub-carriers, and uses new power allocation pattern to allocate power. Simulation indicates scenario 1, scenario 2 and scenario 3 raise the system's total rate on the basis of undertaking the fairness among users’ rates and average packet delay, scenario 4 not only meets users’ rates and average packet delay demands, but also improve the fairness among users’ rates.

One of the newest ways of surgery is known as Minimally Invasive Surgery (MIS), which in spite of its benefits, because of surgeon's tactile sensing omission, causes some problems with detection of arteries and their exact positions in tissue during a surgery. In this study, tactile detection of an artery in tissue has been modeled by finite element method. In this modeling, three 2D models of tissue have been created: tissue, tissue including a tumor, and tissue including an artery. After solving the three models with similar boundary conditions and loadings, the 2D tactile mappings and stress graphs for upper nodes of models, which have the role of transferring tactile data, have been explored. Comparing these results showed that stress graphs of upper nodes of tissue including an artery is time-dependent. However, for two other models it is constant. Then, the effect of variation of different parameters of the model on artery detection such as tissue thickness, artery diameter, and elastic module of artery wall has been studied.

This paper investigates a multi-period rectilinear distance 1-center location problem considering a line-shaped barrier, in which the starting point of the barrier follows the uniform distribution function. In addition, the existing points are sensitive to demands and locations. The purpose of the presented model is to minimize the maximum barrier distance from the new facility to the existing facilities during the finite planning horizon. Additionally, a lower bound problem is generated. The presented model is mixed- integer nonlinear programming (MINLP), however, an optimum solution is reached.

A two-dimensional, unsteady, isothermal and two-phase flow of reactant-product mixture in the airside electrode of proton exchange membrane fuel cells (PEMFC) is studied numerically in the present study. The mixture is composed of oxygen, nitrogen, liquid water and water vapor. The governing equations are two species conservation, a single momentum equation for mobile mixture, liquid mass conservation, and the whole mixture mass conservation. In this study, liquid mass conservation is used to calculate the saturation, so, the effect of liquid phase velocity and also saturation at previous time step are accounted in calculating the next time step saturation. The capillary pressure was used to express the slip velocity between the phases. The strongly coupled equations are solved using the finite volume SIMPLER scheme of Patankar (1984). The computational domain consists of an open area (gas delivery channel), and a porous Gas Diffusion Layer (GDL). A single set of governing equations are solved for both sub domains with respect to each sub domain property. The comparison between the numerical current density and that of experimental (Ticianelli et al. (1988)) shows a good agreement.