1,114 research outputs found
Analysis of a consensus protocol for extending consistent subchains on the bitcoin blockchain
No full textCurrently, an increasing number of third-party applications exploit the Bitcoin blockchain to store tamper-proof records of their executions, immutably. For this purpose, they leverage the few extra bytes available for encoding custom metadata in Bitcoin transactions. A sequence of records of the same application can thus be abstracted as a stand-alone subchain inside the Bitcoin blockchain. However, several existing approaches do not make any assumptions about the consistency of their subchains, either (i) neglecting the possibility that this sequence of messages can be altered, mainly due to unhandled concurrency, network malfunctions, application bugs, or malicious users, or (ii) giving weak guarantees about their security. To tackle this issue, in this paper, we propose an improved version of a consensus protocol formalized in our previous work, built on top of the Bitcoin protocol, to incentivize third-party nodes to consistently extend their subchains. Besides, we perform an extensive analysis of this protocol, both defining its properties and presenting some real-world attack scenarios, to show how its specific design choices and parameter configurations can be crucial to prevent malicious practices
Analysis of a Consensus Protocol for Extending Consistent Subchains on the Bitcoin Blockchain
No full textCurrently, an increasing number of third-party applications exploit the Bitcoin blockchain to store tamper-proof records of their executions, immutably. For this purpose, they leverage the few extra bytes available for encoding custom metadata in Bitcoin transactions. A sequence of records of the same application can thus be abstracted as a stand-alone subchain inside the Bitcoin blockchain. However, several existing approaches do not make any assumptions about the consistency of their subchains, either (i) neglecting the possibility that this sequence of messages can be altered, mainly due to unhandled concurrency, network malfunctions, application bugs, or malicious users, or (ii) giving weak guarantees about their security. To tackle this issue, in this paper, we propose an improved version of a consensus protocol formalized in our previous work, built on top of the Bitcoin protocol, to incentivize third-party nodes to consistently extend their subchains. Besides, we perform an extensive analysis of this protocol, both defining its properties and presenting some real-world attack scenarios, to show how its specific design choices and parameter configurations can be crucial to prevent malicious practices
Il tempio di Guasila in Sardegna. Rilievo del monumento, analisi grafica dei documenti d'archivio e individuazione delle matrici progettuali
No full textIl contributo propone una prima serie di risultati derivanti dall’esame comparato dei documenti d’archivio e del rilievo della chiesa della Vergine Assunta a Guasila,
opera dell’architetto cagliaritano Gaetano Cima. L’edificio, progettato nel 1839 e portato a compimento nel 1852 in luogo della precedente chiesa tardogotica, presenta un disegno simmetrico, impostato su una pianta centrale preceduta da un pronao nel quale sei colonne
doriche affiancate da due pilastri laterali sorreggono un timpano triangolare, e l’utilizzo di matrici e costruzioni geometriche ben definite che richiamano i modelli stilistico-costruttivi del Pantheon, gli insegnamenti proposti dal Palladio1 nel Cinquecento e la Gran Madre di Dio a Torino, progettata dall’architetto Ferdinando Bonsignore nella prima metà dell’Ottocento
An Automatic Alignment Procedure for a Four-Source Photometric Stereo Technique Applied to Scanning Electron Microscopy
No full textDecreased Serum Leptin Levels in Primary Biliary Cirrhosis: A Link between Metabolism and Autoimmunity?
No full textRieger R, Oertelt S, Selmi C, Invernizzi P, Podda M, Gershwin ME. Decreased Serum Leptin Levels in Primary Biliary Cirrhosis: A Link between Metabolism and Autoimmunity? Annals of the New York Academy of Sciences. 2005;1051(1):211-217
Shutdown dose rate assessment with the Advanced D1S method: Development, applications and validation
No full textThe present paper addresses the recent developments and applications of Advanced-D1S to the calculations of shutdown dose rate in tokamak devices. Results of benchmarking with measurements and Rigorous 2-Step (R2S) calculations are summarized and discussed as well as limitations and further developments. The outcomes confirm the essential role of the Advanced-D1S methodology and the evidence for its complementary use with the R2Smesh approach for the reliable assessment of shutdown dose rates and related statistical uncertainties in present and future fusion devices. © 2014 EURATOM-ENEA Association
Applications of McCad for the automatic generation of MCNP 3D models in fusion neutronics
No full textThe Monte Carlo (MC) code MCNP is the reference tool in fusion neutronics, allowing the description and analysis of full and detailed 3D geometry of a tokamak machine. The geometrical models of the components used are typically available through computer aided design (CAD) files: the main benefits of this system are related to its portability and compatibility with several tools commonly used in engineering analyses. However, at the present stage, the information contained in CAD files cannot be directly provided to MC as inputs, because of the different representation scheme used. This issue leads to the necessity to develop interfaces that can translate them into the correct MC geometrical description. McCad is a software developed by the Karlsruhe Institute of Technology (KIT), dedicated to the fully automated generation of MCNP geometrical models from CAD files (STEP, IGES and BREP formats): it's provided with a graphical user interface (GUI) allowing the visualization of the geometries and tools for data exchange and modelling. The present paper summarizes the results of some benchmark tests performed on JET components and a DEMO reactor aimed at the assessment of the suitability of McCad for fusion neutronic applications. The reliability of the conversion algorithm has been evaluated comparing the results of stochastic MCNP volume calculations carried out using the generated models, and the corresponding volumes provided by the CAD kernel of the interface program. Moreover, the consistency of a converted DEMO MCNP model has been verified through particle transport calculations for the estimation of the neutron wall loading poloidal distribution. Several aspects related to the use of the code have been evaluated such as its portability, performances and the impact of the geometric approximation introduced on the neutronic analyses. Furthermore a useful feedback for the optimization and enhancement of the McCad interface has been provided. © 2013 IEEE
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