Sharif Digital Repository

Using an FPGA as a hardware accelerator has been prevalent, to speed up compute intensive workloads. However, employing an accelerator in virtualized environment enhances complexity, because accessing the accelerator from virtual machines has significant overhead and sharing it needs some considerations. We have implemented adequate infrastructure to share an FPGA-based accelerator between multiple virtual machines with negligible access overhead which dynamically implements virtual machines' accelerators. In our architecture each user process from a virtual machine can directly access the FPGA over PCIe link and reconfigure its accelerator in the specified part of FPGA at run-time. The... 

The Analytic 6 D.O.F. dynamic model of a helicopter is developed for 3D computer generated imagery simulator. Analytic expressions for the forces and moments on the various helicopter components are derived. By using the forces and moments equilibrium, helicopter trim point is determined using Newton's method of solving the nonlinear set of trim equations. The equations of motion for the fuselage six degree of freedom are assembled by applying Newton's law of motion relating the applied forces and moments to the resulting translational and rotational acceleration. Visual C++ programming software, utilized as a platform will interact to MATLAB Aircraft Instrument ActiveX and 3DSTATE for... 

In the metal deposition process, the performance of the nozzle is crucial to the quality of clad. Continuous coaxial nozzles are broadly used in this process for repairing two- and three-dimensional parts, because it can create a homogeneous distribution of powder particles. In addition, an inert gas can be applied using this type of nozzles which shields powder particles and laser interaction zone, and prevents the surface from oxidizing at high process temperatures. However, when this type of nozzle is tilted from the vertical axis for cladding non-horizontal surfaces, the effect of gravity on powder particles affects the uniformity of powder distribution at the nozzle outlet. This matter... 

In the metal deposition process, the performance of the nozzle is crucial to the quality of clad. Continuous coaxial nozzles are broadly used in this process for repairing two- and three-dimensional parts, because it can create a homogeneous distribution of powder particles. In addition, an inert gas can be applied using this type of nozzles which shields powder particles and laser interaction zone, and prevents the surface from oxidizing at high process temperatures. However, when this type of nozzle is tilted from the vertical axis for cladding non-horizontal surfaces, the effect of gravity on powder particles affects the uniformity of powder distribution at the nozzle outlet. This matter... 

In order to evaluate the dynamic behavior of floating offshore wind turbines, the authors consider two approaches. A numerical method is used to investigate Tension Leg Platform (TLP) offshore wind turbine response behavior under a parked condition. This code considers nonlinearities due to changes in the tension of tethers. The off-diagonal components of stiffness, damping and mass matrices are considered to calculate coupling. This code solves the nonlinear equation of motion at each time step. However, in order to validate the data generated by the code, a scaled-down model was fully tested in the marine laboratory. The importance of these series of experiments is due to the fact that... 

In this study, the effect of different parameters on the fluid transport in a fractured micromodel has been investigated. All experiments in this study have been conducted in a glass micromodel. Since the state of wetting is important in the micromodel, the wetting experiments have been conducted to determine the state of wetting in the micromodel. The used micromodel was wet by water and non-wet regarding normal decane. The fracture network, distribution of pore size, matrix construction, and injection rate are the most important parameters affecting the process. Therefore, the influence of these parameters was studied using five different patterns (A to E). The obtained results from... 

Scaling imbibition curves are of great importance in the characterization and simulation of oil production from naturally fractured reservoirs. Different parameters such as matrix porosity and permeability, oil and water viscosities, matrix dimensions, and oil/water interfacial tensions have an effective on the imbibition process. Studies on the scaling imbibition curves along with the consideration of different assumptions have resulted in various scaling equations. In this work, using an artificial neural network (ANN) method, a novel technique is presented for scaling imbibition recovery curves, which can be used for scaling the experimental and field-scale imbibition cases. The... 

In this paper, we investigate the problem of detecting and monitoring changes (abnormality) in molecular communication (MC), using the quickest change detection (QCD) schemes. The objective is to watch an environment using a sensor network and make decisions on the time and location of changes based on the received signals from sensors in the fusion center (FC). Such assumptions call for considering spatial and temporal correlations among sensors' transmitting signals. We use the framework of Partially Observable Markov Decision Processes (POMDPs) based on non-homogeneous Markov models. The metric in detection (stopping-time) scenario is to minimize the delay of announcing an abnormality... 

The nature of molecular transmitter imposes some limitations on the molecule production process and its storage. As the molecules act the role of the information carriers, the limitations affect the transmission process and the system performance considerably. In this paper, we focus on the transmitter's limitations, in particular, the limited molecule production rate and the finite storage capacity. We consider a time-slotted communication where the transmitter opens its outlets and releases the stored molecules for a specific time duration to send bit '1' and remains silent to send bit '0'. By changing the Release Duration (RD), we propose an adaptive RD modulation. The objective is to... 

In this paper, we study the problem of cooperative abnormality detection using mobile sensors in a fluidic medium, based on a molecular communication setup. The sensors are injected into the medium to search the environment for the abnormality. To reduce the effects of sensor imperfection, we propose a cooperative scheme where the sensors activate each other by releasing some molecules (i.e., markers), into the medium after they sense an abnormality. A number of fusion centers (FC) are placed at specific locations in the medium, which absorb all sensors arrived at their locations. By observing the states of the received sensors, each FC decides whether an abnormality exists in its... 

The nature of molecular transmitter imposes some limitations on the molecule production process and its storage. As these molecules act the role of the information carriers, their limitation affect the transmission process and the system performance considerably. In this paper, we focus on these limitations at the transmitter, the limited production rate and finite storage capacity. We consider a time-slotted communication where the transmitter opens its outlet and releases the stored molecules for a time duration to send bit '1' and remains silent to send bit '0'. By changing the duration molecules are released, we propose an adaptive pulse-width modulation. The objective is to find the... 

In this paper, we propose a theoretical framework for cooperative abnormality detection and localization systems by exploiting molecular communication setup. The system consists of mobile sensors in a fluidic medium, which are injected into the medium to search the environment for abnormality. Some fusion centers (FC) are placed at specific locations in the medium, which absorb all sensors arrived at their locations, and by observing its state, each FC decides on the abnormality existence and/or its location. To reduce the effects of sensor imperfection, we propose a scheme where the sensors release some molecules (i.e., markers) into the medium after they sense an abnormality. If the goal... 

The job shop scheduling problem with makespan criterion is valuable from both practical and theoretical points of view. This problem has been attacked by most of the well-known meta-heuristic algorithms. Among them, tabu search has emerged as the most effective approach. The proposed algorithm takes advantages of both N1 and N6 neighborhoods. N1 neighborhood is used as a path relinking procedure while N6 neighborhood with its guideposts is applied in a tabu search framework. In addition, a method is presented for updating the topological order, heads and tails in N6 neighborhood. The algorithm is tested on standard benchmark sets, outperformed all previous approaches (include i-TSAB) and... 

This paper presents stage shop problem which is a special case of the general shop. The stage shop is a more realistic generalization of the mixed shop problem. In the stage shop problem, each job has several stages of operations. In order to solve the stage shop problem with makespan objective function, a tabu search algorithm is developed. In addition, an existing lower bound of the job shop is adapted to the new problem and the computational results have been compared to it. The proposed TS algorithm has reached the optimal solutions for about half of the problem instances  

The effectiveness of the local search algorithms for shop scheduling problems is proved frequently. Local search algorithms like tabu search use neighborhood structures in order to obtain new solutions. This paper presents a new neighborhood for the job shop scheduling problem. In this neighborhood, few enhanced conditions are proposed to prevent cycle generation. These conditions allow that the neighborhood encompasses larger number of solutions without increasing the order of computational efforts  

This paper presents a special case of the general shop called stage shop problem. The stage shop is a more realistic generalization of the mixed shop problem. In the stage shop problem, each job has several stages of operations. In order to solve the stage shop problem with makespan objective function, an existing neighborhood of job shop is used. In this neighborhood, few enhanced conditions are proposed to prevent cycle generation. In addition, a new neighborhood for operations that belong to the same job is presented. These neighborhoods are applied to the stage shop problem in a tabu search framework. A genetic algorithm is used to obtain good initial solutions. An existing lower bound... 

This paper presents a special case of the general shop called partial job shop problem. The partial job shop is a more realistic generalization of the mixed shop problem. The problem is formulated as a mixed integer programming model. A scatter search algorithm combined with tabu search and path relinking is used to tackle this problem with makespan criterion. The computational experiments are performed on some problem instances. The results are compared with a lower bound and the effectiveness of the algorithm is shown  

The job shop scheduling problem is a difficult combinatorial optimization problem. This paper presents a hybrid algorithm which combines global equilibrium search, path relinking and tabu search to solve the job shop scheduling problem. The proposed algorithm used biased random sampling to have a better covering of the solution space. In addition, a new version of N6 neighborhood is applied in a tabu search framework. In order to evaluate the algorithm, comprehensive tests are applied to it using various standard benchmark sets. Computational results confirm the effectiveness of the algorithm and its high speed. Besides, 19 new upper bounds among the unsolved problems are found  

Flow velocity is an important characteristic of the fluidic mediums. In this article, we introduce a molecular based flow velocity meter consisting of a molecule releasing node and a receiver that counts these molecules. We consider both flow velocity detection and estimation problems, which are employed in different applications. For the flow velocity detection, we obtain the maximum a posteriori (MAP) decision rule. To analyze the performance of the proposed flow velocity detector, we obtain the error probability, its Gaussian approximation and Chernoff information (CI) upper bound, and investigate the optimum and sub-optimum sampling times accordingly. We show that, for binary hypothesis,...