932 research outputs found

    Traffic Offloading/Onloading in Multi-RAT Cellular Networks

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    We analyze next generation cellular networks, offering connectivity to mobile users through multiple radio access technologies (RATs), namely LTE and WiFi. We develop a framework based on the Markovian agent formalism, which can model several aspects of the system, including user traffic dynamics and radio resource allocation. In particular, through a mean-field solution, we show the ability of our framework to capture the system behavior in flash-crowd scenarios, i.e., when a burst of traffic requests takes place in some parts of the network service area. We consider a distributed strategy for the user RAT selection, which aims at ensuring high user throughput, and investigate its performance under different resource allocation scheme

    Survivability study of a Water Cleaning Facility using Fluid Stochastic Petri Nets

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    This paper investigates the survivability of a water cleaning facility using Fluid Stochastic Petri Nets (FSPNs). Water cleaning facilities are responsible for providing drinking water to a specific district. The provided service is very important and makes such facilities belong to a nation's critical infrastructures. Therefore, such a facility should be able to recover in a timely manner after the occurrence of disasters. The use of FSPNs in survivability research is new and promising due to its general applicability. In this paper we model and analyze the survivability of of the last phases of the water cleaning process in a Dutch water company. Analysis results identify the weaknesses of the process and redundancy is suggested to improve the survivability

    Grapevine root transformation with Agrobacterium rhizogenes

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    Grapevine shoots were obtained from tissue cultures of cvs Barbera, Moscato bianco and Nebbiolo; their stems were wounded and inoculated with the following strains of Agrobacterium rhizogenes. A4, 8196, NCPP 2659, and 15834. Root production at the inoculation site was obtained in about 25% of the stems of all cultivars with all the bacterial strains, with the exception of NCPP 2659, which gave a lower root proliferation rate. Cultures of roots obtained after inoculation were established and their growth was enhanced by some media and by addition of cytokinins and auxins to the medium. Root cultures obtained after inoculation with the strain 8196 were genetically transformed, as shown by opine production. In contrast, opines were seldom detected in the root cultures obtained with the other bacterial strains. Light microscope observation showed that the cortex of transformed roots has more cell layers and a larger average cell size than in normal roots

    Performance Analysis of the ARIA Adaptive Media Processing Workflows using Colored Petri Nets

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    AbstractMultimedia systems are one of the most complex and interesting applications that are nowadays proposed to the users. Their complexity derives mainly from the fact that multimedia systems have to process huge amounts of data, while respecting real-time deadlines. For this reason performance evaluation of the underlaying workflow is a key issue in the design process of a new Multimedia system.In this paper we consider the ARchitecture for Interactive Arts (ARIA), an adaptive media processing workflow, developed at the Arizona State University, and outline a semi-automatic procedure to translate its specification into Colored Petri Nets. We then provide guidelines on how to compute the parameters for the performance models, and apply the proposed methodology to a realistic example of a face recognition application

    Improved control of water loss from micropropagated grapevines (Vitis vinifera cv. Nebbiolo)

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    Micropropagated plantlets are generally susceptible to rapid desiccation when exposed to reduced relative humidity and require a costly acclimatization procedure. Detached leaves of micropropagated Vitis vinifera, cv. Nebbiolo, plantlets were used to evaluate the relative contribution of leaf cuticle and stomata to water loss. Water loss occurred mainly from the abaxial surface of detached leaves; moreover, a large majority of stomata was still open 3 h after exposure to 63 % RH. An indirect estimation of epicuticular wax suggested a lower wax deposition for micropropagated plantlets compared to acclimatized and field-grown plants of the same clone. A previously developed method to produce hardened micropropagated plants was adopted: 1 mg(.)l(-1) paclobutrazol (PBZ) was added to the medium and culture vessels with reduced relative humidity (rRH) were used during the last stage of micropropagation. Under our experimental conditions, rRH was more effective to reduce transpiration than PBZ; a combination of both treatments improved plant survival during acclimatization.
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