Voici les éléments 1 - 7 sur 7
- PublicationMétadonnées seulementA4mesh : Connecting remote sites(2012-3-1)
;Jamakovic-Kapic, A. ;Awander, M. ;Braun, T. ; ; ;Schwanebeck, J.Staub, T.Developments in A4-Mesh have turned wireless mesh networks into a valuable technology for Swiss institutions of higher education. Large numbers of research projects in different areas, like climate research and geology, will profit from an easily deployable outdoor wireless network that also supports mechanisms for authentication, authorization, accounting and auditing (A4) functionalities.
- PublicationAccès libreIntegrating hydrological modelling, data assimilation and cloud computing for real-time management of water resources(2017-7-1)
; ;Kurtz, Wolfgang ; ; ; ; ;Braun, Torsten ; ;Vereecken, Harry ;Sudicky, Edward ;Franssen, Harrie-Jan HendricksOnline data acquisition, data assimilation and integrated hydrological modelling have become more and more important in hydrological science. In this study, we explore cloud computing for integrating field data acquisition and stochastic, physically-based hydrological modelling in a data assimilation and optimisation framework as a service to water resources management. For this purpose, we developed an ensemble Kalman filter-based data assimilation system for the fully-coupled, physically-based hydrological model HydroGeoSphere, which is able to run in a cloud computing environment. A synthetic data assimilation experiment based on the widely used tilted V-catchment problem showed that the computational overhead for the application of the data assimilation platform in a cloud computing environment is minimal, which makes it well-suited for practical water management problems. Advantages of the cloud-based implementation comprise the independence from computational infrastructure and the straightforward integration of cloud-based observation databases with the modelling and data assimilation platform.
- PublicationMétadonnées seulementSurvey on Load Balancing in Peer-to-Peer Distributed Hash Tables(2014)
; ; ;Serbu, SabinaPeer-to-peer systems represent a radical shift from the classical client-server paradigm in which a centralized server processes requests from all clients. In a peer-to-peer (P2P) system, every "peer" can play the role of a client and a server at the same time, hence sharing responsibilities among all parties. As in practice some peers or connecting links may be heavily loaded in comparison to others, load balancing algorithms are necessary to ensure a fair distribution of the load among participating peers. In this survey, we present load management solutions in P2P systems. According to the level at which they operate, we classify the different approaches into three categories: object placement, routing protocol, and underlay. The first two approaches tackle information lookup and retrieval in the overlay network, while the last one addresses traffic imbalance at the level of the underlying network.
- PublicationMétadonnées seulementNetwork Performance of the JBoss Application Server(: IEEE, 2013-10-22)
;Benothman, Nabil ;Clere, Jean-Frederic ; ;Maucherat, RemyJBoss Application Server (AS) uses java.io and the Apache Portable Runtime (APR) project to provide its HTTP connectors. Due to new features of upcoming specifications of the Java Enterprise Edition (Java EE), the existing connectors shall be replaced by modern non blocking Input/Outputs (I/Os). In this study, we review some modern I/O frameworks such as NIO.2 introduced by Java SE 7 and XNIO3 developed by JBoss. We compare their network performance by running a series of stress tests on client-server applications of limited functionality. As a result, we select NIO.2 as the most appropriate framework to specify and implement a new JBoss connector. Finally, we compare our newly implemented Java connector against the existing APR-based one by means of network performance measures.
- PublicationAccès libreReal-time Environmental Monitoring for Cloud-based Hydrogeological Modeling with HydroGeoSphere(: IEEE Computer Society, 2014)
; ; ; ; ; ;Jamakovic-Kapic, A. ;Braun, T.Maffioletti, S.This paper describes an architecture for real-time environmental modeling. It consists of a wireless mesh network equipped with sensors and a cloud-based infrastructure to perform real-time environmental sim- ulations using a physics-based model combined with an Ensemble Kalman Filter. The purpose of the system is to optimize groundwater abstraction close to a river. These initial studies demonstrate that the cloud infrastructure can simultaneously compute a large number of simula- tions, thus allowing for the implementation of Ensemble Kalman Filters in real-time.
- PublicationAccès libreWireless Mesh Networks and Cloud Computing for Real Time Environmental Simulations(: Springer, 2014-4-22)
; ; ; ; ;Predicting the influence of drinking water pumping on stream and groundwater levels is essential for sustainable water management. Given the highly dynamic nature of such systems any quantitative analysis must be based on robust and reliable modeling and simulation approaches. The paper presents a wireless mesh-network framework for environmental real time monitoring integrated with a cloud computing environment to execute the hydrogeological simulation model. The simulation results can then be used to sustainably control the pumping stations. The use case of the Emmental catchment and pumping location illustrates the feasibility and effectiveness of our approach even in harsh environmental conditions.
- PublicationMétadonnées seulementShibboleth based Authentication, Authorization, Accounting and Auditing in Wireless Mesh Networks(: IEEE, 2011-10-22)
; ;We present the basic architectural elements of the Captive Portal integrating Shibboleth based Authentication, Authorization, Accounting and Auditing into Wireless Mesh Networks. The Captive Portal is built upon the SWITCHaai/Shibboleth architecture especially designed to protect web based services. The architecture is secure, eavesdropping protected and does not require any specialized software installation on the client side.