Search results for "SIMULATION"

An Integrated Multi-service Software Simulation Platform: SIMPSONS Architecture

2005

This paper describes SIMPSONS (SIp and MPls Simulations On NS-2), which is a software platform for simulating multiple network scenarios, such as Telephony Over IP (TOIP), and multi-services networks extending the functionalities of Network Simulator NS-2. The innovative aspects of SIMPSONS is the complete integration of control protocols and traffic engineering mechanisms inside the same simulation tool. In fact, next generation networks must meet basically two fundamental requirements: support of Quality of Service (QoS) and Traffic Engineering (TE) functionalities. SIMPSONS is able to simulate DiffServ, MPLS, OSPF and SIP and their interaction in everything TOIP scenario. So with this po…

Is Admission-Controlled Traffic Self-Similar?

2002

It is widely recognized that the maximum number of heavy-tailed flows that can be admitted to a network link, while meeting QoS targets, can be much lower than in the case of markovian flows. In fact, the superposition of heavy-tailed flows shows long range dependence (self-similarity), which has a detrimental impact on network performance. In this paper, we show that long range dependence is significantly reduced when traffic is controlled by a Measurement-Based Admission Control (MBAC) algorithm. Our results appear to suggest that MBAC is a value added tool to improve performance in the presence of self-similar traffic, rather than a mere approximation for traditional (parameter-based) ad…

A Proposal for Agent Simulation of Peer Review

2010

Peer review lies at the core of current scientific research. It is composed of a set of social norms, practices and processes that connect the abstract scientific method with the society of people that apply the method. As a social construct, peer review should be understood by building theory-informed models and comparing them with data collection. Both these activities are evolving in the era of automated computation and communication: new modeling tools and large bodies of data become available to the interested researcher. In this paper, starting from abstract principles, we develop and present a model of the peer review process. We also propose a working implementation of a subset of t…

The min-max close-enough arc routing problem

2022

Abstract Here we introduce the Min-Max Close-Enough Arc Routing Problem, where a fleet of vehicles must serve a set of customers while trying to balance the length of the routes. The vehicles do not need to visit the customers, since they can serve them from a distance by traversing arcs that are “close enough” to the customers. We present two formulations of the problem and propose a branch-and-cut and a branch-and-price algorithm based on the respective formulations. A heuristic algorithm used to provide good upper bounds to the exact procedures is also presented. Extensive computational experiments to compare the performance of the algorithms are carried out.

Heuristics for the bi-objective path dissimilarity problem

2009

In this paper the path dissimilarity problem is considered. The problem has previously been studied within several contexts, the most popular of which is motivated by the need to select transportation routes for hazardous materials. The aim of this paper is to formally introduce the problem as a bi-objective optimization problem, in which a single solution consists of a set of p different paths, and two conflicting objectives arise, on one hand the average length of the paths must be kept low, and on the other hand the dissimilarity among the paths in the set should be kept high. Previous methods are reviewed and adapted to this bi-objective problem, thus we can compare the methods using th…

Comparing multicriteria methods in the context of environmental problems

1998

Abstract The present paper gives an analysis of the use of ELECTRE III, PROMETHEE I, II, and SMART decision-aids in the context of four different real applications to environmental problems in Finland. These methods are widely used decision-aids in the real planning processes. The purpose of this study is to define the differences of these methods and the results obtained with them, and in this way also to consider their applicability in aiding environmental decision-making. Furthermore, a comparison of the methods based on a set of randomly generated problems is carried out. The choice in practice will not be easy; PROMETHEE does not differ much from SMART with linear value functions, and …

Application of adaptive models for the determination of the thermal behaviour of a photovoltaic panel

2013

The use of reliable forecasting models for the PV temperature is necessary for a more correct evaluation of energy and economic performances. Climatic conditions certainly have a remarkable influence on thermo-electric behaviour of the PV panel but the physical system is too complex for an analytical representation. A neural-network-based approach for solar panel temperature modelling is here presented. The models were trained using a set of data collected from a test facility. Simulation results of the trained neural networks are presented and compared with those obtained with an empirical correlation.

Stability of the performance of thin film modules during one year of operation

2012

At the University of Agder in Grimstad, Southern Norway, a test bench for photovoltaic modules is in operation since December 2010. Currently, various c-Si as well as aSi, CIS and HIT modules are under investigation. This project is part of the Norwegian contribution to IEA PVPS Task13. The paper focuses on the stability of the modules' MPP-performance in the course of one year. For this purpose, data on the DC response are logged together with irradiance and module temperature at one-minute intervals. Data analysis is performed in monthly blocks. The modeling involves two steps. First, the short-circuit current is expressed as function of irradiance and module temperature. Then, the MPP po…

Closure to Using Hydrus 2-D Simulation Model to evaluate Wetted Soil Volume in Subsurface Drip Irrigation Systems.

2008

Genetic structure in the Mediterranean seagrass Posidonia oceanica: disentangling past vicariance events from contemporary patterns of gene flow

2010

The Mediterranean Sea is a two-basin system, with the boundary zone restricted to the Strait of Sicily and the narrow Strait of Messina. Two main population groups are recognized in the Mediterranean endemic seagrass Posidonia oceanica, corresponding to the Western and the Eastern basins. To address the nature of the East-West cleavage in P. oceanica, the main aims of this study were: (i) to define the genetic structure within the potential contact zone (i.e. the Strait of Sicily) and clarify the extent of gene flow between the two population groups, and (ii) to investigate the role of present water circulation patterns vs. past evolutionary events on the observed genetic pattern. To achiev…