Community networks are crowd-sourced IP networks that evolved into regional-scale computing platforms. This has led to adapting the cloud computing model for services that can operate and use computing resources inside a community network. The network and computing infrastructure is contributed by individuals, companies, organizations and maintained by its members. Community cloud devices are often low-capacity computing devices, such as home gateways or cabinet servers, with limited capabilities. These devices are used to install and operate specific personal or community services, but can be turned into multi-purpose execution environments applying machine or operating system (container) virtualization. However that requires addressing the problems of resource sharing in low-capacity devices, related to predictable performance and isolation. Our comparative analysis with the current infrastructure in community networks gives evidence about how devices can concurrently run multiple services, the trade offs between the number and resource requirements of services and the degradation of quality that services may suffer.
High intensity discharge lamps with magnetic ballast are energy-efficient lighting devices commonly used in industrial and public installations. These lamps can be important pollution loads, and their harmonic modeling has been extensively studied considering linear magnetic ballast and square arc voltage waveform. Previous assumptions can be far from describing actual lamp behavior, affecting the accuracy of the model. This paper proposes a PSpice model of high intensity discharge lamps considering both the non-linear behavior of the magnetic ballast and the non-square waveform of the arc voltage. The PSpice model is successfully validated with lab experimental measurements. (C) 2014 Elsevier B.V. All rights reserved.
This study focuses on the importance of quantifying the effect of prefetching on the interconnection network of a multiprocessor chip. This kind of microarchitectural effects are often quantified using simulators. However, if prefetching traffic in a CMP (Chip MultiProcessor) system is to be accurately evaluated, simulators should simulate not only the memory hierarchy module and the multicore system, but also the network-on-chip. Unfortunately, no open-source simulator is able to evaluate all these elements at the same time. This paper describes how to develop a prefetching module for the gem5 CMP simulator and how to integrate this into the Ruby memory system. Moreover, by using the infrastructure developed in this study, this paper shows the importance of taking the network effect in prefetching-related studies into account, in order for accurate results to be obtained: not doing so may lead to mistaken conclusions. For this purpose, we have carried out a detailed analysis of the behavior of three different prefetching engines, providing not only the typical statistics for instructions per cycle and the miss rate, but also specific network and prefetching statistics.
This paper describes a conceptual model intended to be applied in a general approach to the micro-simulation of hub airports terminals. The proposed methodology is illustrated with the development of a simulation model originally intended to help in the design of the new terminal at Barcelona International Airport. This model represents in detail, among many other elements, passengers’ flows in the different areas of these complex facilities. Agent-based simulation techniques were included to represent the different actors’ behaviors, and a formal representation of the model using Specification and Description Language (SDL) was used to represent the complexity of all the system elements. To pre-process a diverse and considerable amount of raw data provided by airport designers and other sources to feed the simulation environment Flight Planner Manager was developed as a toolkit to parameterize the different model factors and to generate required specific input data. This project was conducted over 3 years leading to the development of a system not only conceived to assess in the airport initial design process but also to constitute a recurrent decision taking instrument to dynamically optimize terminal management and operations.
In many countries worldwide, the energy demand is growing faster than the transmission capacity. However, due to environmental constrains, social concerns and financial costs, the construction of new power transmission lines is an arduous task. In addition, power transmission systems are often loaded close to their nominal values. Therefore, improving power transmission system efficiency and reliability is a matter of concern. This work deals with a 400 kV, 3000 A, 50 Hz extra-high-voltage expansion substation connector used to connect two substation bus bars of 150 mm diameter each. This substation connector has four aluminum wires which provide the conductive path between both bus bars. Preliminary tests showed an unequal current distribution through the wires which was mainly attributed to the proximity effect. A three-dimensional finite elements method approach was applied to improve the design and evaluate the electromagnetic and thermal behavior of both the original and improved versions of the connector. Experimental tests made under laboratory conditions have validated the accuracy of the simulation method presented in this paper, which may be a valuable tool to assist the design process of substation connectors, therefore allowing improving both the thermal performance and reliability of the redesigned connectors.
This paper shows the capabilities of applying the three-dimensional finite element method (3D-FEM) for designing complex-shaped substation connectors to operate at 765 kVRMS AC. To check this methodology, it was analyzed the feasibility of upgrading a 400 kVRMS substation connector to operate at 765 kVRMS. However, both experimental and simulation results conducted according to the ANSI/NEMA CC 1-2009 standard concluded that although it passed the visual corona test, to ensure a wide safety margin it was desirable an improvement of the electrical behavior of such connector. It was shown that FEM results allowed detecting the peak stress points of the connector regarding the electrical stress thus allowing applying a corrective action. Then, two possible solutions were analyzed, i.e. the use of corona shields and the redesign of the connector assisted by 3D-FEM simulations. Results presented in this work show that both approaches have an excellent behavior in reducing the electric field strength on the connector surface. However, to make the final decision, the production cost of both alternatives was analyzed, thus favoring the redesign option. Next, the redesigned version of the substation connector was manufactured and tested. Experimental results conducted in a high voltage laboratory verified the effectiveness of the methodology and the potential of the proposed system to act as an advanced design tool for optimizing the behavior of complex-shaped substation connectors. Thus, this system allows assisting efficiently the design process while permitting constraining the economic costs
Llatser, I.; Demiray, D.; Albert Cabellos-Aparicio; Altilar, D.; Alarcon, E. Simulation modelling practice and theory Vol. 42, p. 210-222 DOI: 10.1016/j.simpat.2013.11.004 Data de publicació: 2014-03-01 Article en revista
Diffusion-based molecular communication is a promising bio-inspired paradigm to implement nanonetworks, i.e., the interconnection of nanomachines. The peculiarities of the physical channel in diffusion-based molecular communication require the development of novel models, architectures and protocols for this new scenario, which need to be validated by simulation. N3Sim is a simulation framework for nanonetworks with transmitter, receiver, and harvester nodes using Diffusion-based Molecular Communication (DMC). In DMC, transmitters encode the information by releasing molecules into the medium, thus varying their local concentration. N3Sim models the movement of these molecules according to Brownian dynamics, and it also takes into account their inertia and the interactions among them. Harvesters collect molecules from the environment to reuse them for later transmissions. Receivers decode the information by sensing the particle concentration in their neighborhood. The benefits of N3Sim are multiple: the validation of channel models for DMC and the evaluation of novel modulation schemes are just a few examples. (C) 2013 Elsevier B.V. All rights reserved.
The use of wireless networks is having an ever greater impact on systems controlling automation, industrial manufacturing, distributed control and supervision. Wireless technologies in particular have penetrated quickly the area of control of public utilities networks, and typical examples of this are remote control and supervision of large water, gas or electricity distribution networks. These types of networks are usually formed of a central station and different remote stations, and remote clients who are able to remotely monitor or even control the working of the system. To improve the use of the system, the remote stations must have the capacity to exchange information between each other and with the central station. The spontaneous generation of wireless networks in remote stations to exchange information between workers is a possible solution. Taking into account the characteristics of this type of monitoring system, the paper has proposed a scenario (number of nodes, area size, mobility) and has modeled, using stochastic activity networks (SAN), the operation of an ad hoc network that uses a reactive routing protocol to determine if the network is able to offer the typical services of these facilities (images or video streaming and alerts).
In this work we present a new method for the modeling and simulation study of a photovoltaic grid connected system and its experimental validation. This method has been applied in the simulation of a grid connected PV system with a rated power of 3.2 Kwp, composed by a photovoltaic generator and a single phase grid connected inverter. First, a PV module, forming part of the whole PV array is modeled by a single diode lumped circuit and main parameters of the PV module are evaluated. Results obtained for the PV module characteristics have been validated experimentally by carrying out outdoorI–Vcharacteristic measurements. To take into account the power conversion efficiency, the measured AC output power against DC input power is fitted to a second order efficiency model to derive its specific parameters.The simulation results have been performed through Matlab/Simulink environment. Results has shown good agreement with experimental data, whether for theI–Vcharacteristics or for the whole operating system. The significant error indicators are reported in order to show the effectiveness of the simulation model to predict energy generation for such PV system.
Xhafa, F.; Barolli, A.; Sánchez, C.; Barolli, L. Simulation modelling practice and theory Vol. 19, num. 10, p. 2276-2284 DOI: 10.1016/j.simpat.2010.08.014 Data de publicació: 2011-11 Article en revista
Riba, J.; Garcia, A.; Cusido, J.; Delgado Prieto, M. Simulation modelling practice and theory Vol. 19, num. 9, p. 1918-1932 DOI: 10.1016/j.simpat.2011.05.005 Data de publicació: 2011-10-01 Article en revista
Most of current research in Grid computing is still focused on the improvement of the performance of Grid schedulers. However, unlike traditional scheduling, in Grid systems there are other important requirements to be taken into account. One such a requirement is the secure scheduling, namely achieving an efficient allocation of tasks to reasonable trustful resources. In this paper we formalize the Grid scheduling problem as a non-cooperative non-zero sum game of the Grid users in order to address the security requirements. The premise of this model is that in a large-scale Grid, the cooperation among all users in the system is unlikely to happen. The users’ cost of playing the game is interpreted as a total cost of the secure job execution in Grid. The game cost function is minimized, at global (Grid) and local (users) levels, by using four genetic-based hybrid meta-heuristics. We have evaluated the proposed model under the heterogeneity, the large-scale and dynamics conditions using a Grid simulator. The relative performance of four hybrid schedulers is measured by the makespan and flowtime metrics. The obtained results suggested that it is more resilient for the Grid users to pay some additional scheduling cost, due to verification of the security conditions, instead of taking the risk of assigning their tasks to unreliable resources
Junyent-Ferré, A.; Gomis-Bellmunt, O.; Sumper, A.; Sala, M.; Mata, M. Simulation modelling practice and theory Vol. 18, num. 9, p. 1365-1381 DOI: 10.1016/j.simpat.2010.05.018 Data de publicació: 2010-10 Article en revista
Sorli, M.; Gastaldi, L.; Codina-Macia, Esteban; De Las Heras, S.A. Simulation modelling practice and theory Vol. 7, num. 5-6, p. 589-602 DOI: 10.1016/S0928-4869(99)00012-9 Data de publicació: 1999-12 Article en revista