1,720,997 research outputs found
Field Data Based Modeling of Sender Based Message Logging Protocols for Supercomputers Checkpointing
No full textCheckpointing is today's common mean for dealing with transient failures in supercomputers. However, the effectiveness of checkpointing and recovery protocols under the assumption that failures may happen during their operation is not well understood. We present an evaluation of the checkpointing and recovery based on Sender Based Message Logging protocols (SBML). We evaluate it by means of a model which is gathered from an extensive field data campaign performed on the SCOPE supercomputer at the University of Naples. A comprehensive model is built to evaluate reliability, scalability and performance of SBML. The proposed model takes into account failures during the checkpointing and recovery. Result provide insights on the limit of the number of nodes that can be allocated to the same job considering i) the overhead for the distributed coordination for rollback, and ii) network resources (e.g. bandwidth)
On Data Dissemination for Large-Scale Complex Critical Infrastructures
No full textMiddleware plays a key role for the achievement of the mission of future largescalecomplexcriticalinfrastructures, envisioned as federations of several heterogeneous systems over Internet. However, available approaches for datadissemination result still inadequate, since they are unable to scale and to jointly assure given QoS properties. In addition, the best-effort delivery strategy of Internet and the occurrence of node failures further exacerbate the correct and timely delivery of data, if the middleware is not equipped with means for tolerating such failures.
This paper presents a peer-to-peer approach for resilient and scalable datadissemination over large-scalecomplexcriticalinfrastructures. The approach is based on the adoption of epidemic dissemination algorithms between peer groups, combined with the semi-active replication of group leaders to tolerate failures and assure the resilient delivery of data, despite the increasing scale and heterogeneity of the federated system. The effectiveness of the approach is shown by means of extensive simulation experiments, based on Stochastic Activity Networks
iCAAS: interoperable and Configurable Architecture for Accessing Sensor networks
No full textThe increasing use of wireless sensor networks (WSNs) calls for solutions for mastering the complexity due to WSN heterogeneity and differentiated user needs. This paper presents an architecture, named iCAAS, designed to collect, to store, to manage and to make available to users data received from heterogeneous WSNs. The aim of the architecture is to adaptively deliver data to users depending on their specific interests and irrespective of adopted terminals (e.g., mobile device, workstation, ...) and of sensor networks details. The contribution of the paper is twofold. First we detail the requirements that these types of architectures should meet to fill the gap between sensors details and users needs. Second, we describe the structural organization of the proposed architecture, designed by taking into account the defined requirements. Implementation details and case studies are also provided, showing the effectiveness of the architecture when used in real world application scenarios
Automated Generation of Performance and Dependability Models for the Assessment of Wireless Sensor Networks
No full textWireless Sensor Networks (WSNs) are widely recognized as a promising solution to build next-generation monitoring
systems. Their industrial uptake is however still compromised by the low level of trust on their performance and dependability.
Whereas analytical models represent a valid mean to assess nonfunctional properties via simulation, their wide use is still limited by the complexity and dynamicity of WSNs, which lead to unaffordable modeling costs. To reduce this gap between research
achievements and industrial development, this paper presents a framework for the assessment of WSNs based on the automated
generation of analytical models. The framework hides modeling details, and it allows designers to focus on simulation results to drive
their design choices. Models are generated starting from a high-level specification of the system and by a preliminary characterization
of its fault-free behavior, using behavioral simulators. The benefits of the framework are shown in the context of two case studies,
based on the wireless monitoring of civil structures
Modeling and Assessing the Dependability of Wireless Sensor Networks
No full textThis paper proposes a flexible framework for dependability
modeling and assessing of Wireless Sensor Networks
(WSNs). The framework takes into account network related
aspects (topology, routing, network traffic) as well
as hardware/software characteristics of nodes (type of sensors,
running applications, power consumption). It is composed
of two basic elements: i) a parametric Stochastic
Activity Networks (SAN) failure model, reproducing WSN
failure behavior as inferred from a detailed Failure Mode
Effect Analysis (FMEA), and ii) an external library reproducing
network behavior on behalf of the SAN model. This
library specializes the SAN model by feeding it with quantitative
parameters obtained by simulation or by experimental
campaigns; it is also in charge of updating the network
state in response to failure events during the simulation
(e.g., routing tree updated due to node failures).
The framework is thus suited to evaluate the dependability
of several WSNs, with different topologies, routing algorithms,
hardware/software platforms, without requiring
any changes to its structure. The use of the external library
makes the model simpler, decoupling the network behavior
from the failure behavior. Simulation experiments are
discussed that provide a quantitative evaluation of WSN
dependability for a sample scenario: results show how
the proposed framework supports WSN developers to find
proper cost-reliability trade-offs for the system being deployed
Microalgae cross-fertilization: short-term effects of Galdieria phlegrea extract on growth, photosynthesis and enzyme activity of Chlorella sorokiniana cells
No full textGaldieria spp. (Rhodophyta) are polyextremophile microalgae known for their important antioxidant properties in different biological systems. Nowadays, the beneficial and bio-stimulant effect of microalgal extracts is widely tested on crops. Here, for the first time, potential positive effects of aqueous extracts from Galdieria were tested on a second microalgal culture systems. Chlorella sorokiniana cultures were supplemented with Galdieria phlegrea extracts (EC) and the short-term (48 h) effects of extract addition on growth and biochemical and physiological parameters were monitored and compared to those of non-supplemented Chlorella (CC). Growth of Chlorella was improved in EC as shown by higher optical density and cells number in the enriched cultures. In addition, EC appreciably increased the pigments (chlorophyll (a and b) and carotenoids) contents of Chlorella cells. Increase of photosynthetic pigments was associated with higher photosynthesis and lower non-radiative dissipation of light in EC as indicated by chlorophyll fluorescence parameters. Reduced activities of antioxidant enzymes (SOD, CAT and APX), but increased total antioxidant capacity (ABTS) were observed in EC, suggesting that this culture was under a low oxidative status, but can activate antioxidant defences if exposed to oxidative stress. In conclusion, a short-term positive effect of the addition of G. phlegrea extracts on growth and physiology of C. sorokiniana was demonstrated
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