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Search Results: 1 - 10 of 3770 matches for " Roman Schlegel "
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ReDS: A Framework for Reputation-Enhanced DHTs
Ruj Akavipat,Mahdi N. Al-Ameen,Apu Kapadia,Zahid Rahman,Roman Schlegel,Matthew Wright
Computer Science , 2012, DOI: 10.1109/TPDS.2013.231
Abstract: Distributed Hash Tables (DHTs) such as Chord and Kademlia offer an efficient solution for locating resources in peer-to-peer networks. Unfortunately, malicious nodes along a lookup path can easily subvert such queries. Several systems, including Halo (based on Chord) and Kad (based on Kademlia), mitigate such attacks by using a combination of redundancy and diversity in the paths taken by redundant lookup queries. Much greater assurance can be provided, however. We describe Reputation for Directory Services (ReDS), a framework for enhancing lookups in redundant DHTs by tracking how well other nodes service lookup requests. We describe how the ReDS technique can be applied to virtually any redundant DHT including Halo and Kad. We also study the collaborative identification and removal of bad lookup paths in a way that does not rely on the sharing of reputation scores --- we show that such sharing is vulnerable to attacks that make it unsuitable for most applications of ReDS. Through extensive simulations we demonstrate that ReDS improves lookup success rates for Halo and Kad by 80% or more over a wide range of conditions, even against strategic attackers attempting to game their reputation scores and in the presence of node churn.
The decreasing political rewards of education in Brazil
Brazilian Political Science Review (Online) , 2010,
Abstract: the conventional perspective in political science expects a strong association between education and political behaviour favourable for democratic coexistence. this approach also infers that increases in a nation's educational attainment levels will be accompanied by sustained gains in attitudes such as political engagement and democratic support. these hypotheses have been reviewed and tested for brazil, with analyses of surveys conducted between 1989 and 2006. the evidence confirms the conventional perspective when a single point in time is observed and dimensions of associativism are excepted. however, longitudinal analysis between the two extremities of the period revealed decreasing rewards for schooling added up by different levels of education - particularly the upper secondary - in several dimensions of participation and support for democratic principles.
Internauta brasileiro: perfil diferenciado, opini?es indiferenciadas
Schlegel, Rogerio;
Revista de Sociologia e Política , 2009, DOI: 10.1590/S0104-44782009000300011
Abstract: this article attempts to contribute to improving our understanding of the relationship between internet use, on the one hand, and the political participation of citizens, on the other. we emphasize the factors that determine regular internet use and user profiles in relation to political values and participation. analysis of data from the latinobarómetro 2007 survey indicate age and educational level as primary determinants of internet use in brazil. occupation, as well as a proxy used for income did not have a consistent impact on people's probabilities of connecting, thus contrasting brazilian data with data on argentine and chilean cases. at the same time, the public belonging to the on-line community demonstrated greater mobilization, in terms of traditional forms of political participation, and little differentiation in terms of political opinions, when compared to non-users of this new technology. this evidence suggests that connection to the digital world tends to enhance the voice of segments of the population that already enjoy privileged access to government and public policy managers, particularly given their cultural capital, although there are some signs of existing opportunities for other segments of society sectors. it also indicates that the importance of the country's "digital divide" can be relativized, since internauts do not hold opinions that are significantly different from those of the rest of the population.
Sobre a incompreensibilidade
Friedrich Schlegel
Alea : Estudos Neolatinos , 2011, DOI: 10.1590/s1517-106x2011000200010
Communication Patterns as Key Towards Component-Based Robotics
Christian Schlegel
International Journal of Advanced Robotic Systems , 2008,
Abstract: Vital functions of mobile robots are provided by software and software dominance is still growing. Mastering the software complexity is not only a demanding but also indispensable task towards an operational robot. Nevertheless, well-known and even always needed algorithms are often implemented from scratch over and over again instead of being reused as off-the-shelf components. A major reason is the lack of a framework that allows to compose robotics software out of standardized components without already prescribing a robotics architecture. Whereas Component Based Software Engineering (CBSE) is an approach to make a shift from implementation to composition, the general CBSE approach does not give any hints on how to ensure that independently provided components finally fit together as reusable components. This paper introduces a small set of communication patterns as basis for all intercomponent interactions. Since all externally visible interfaces of components are composed out of the same set of communication patterns, these are the key towards a stringent interface semantics. Generic communication patterns enforce decoupling of components and ensure composability by restricting the diversity of interfaces. The SmartSoft framework as one implementation of this approach already proved its adequacy in many projects.
EFOMP: the European roof for medical physics
W Schlegel
Biomedical Imaging and Intervention Journal , 2007, DOI: 10.2349/biij.3.3.e32
Central Nervous System Toxicity of Chemotherapy
Schlegel U
European Association of NeuroOncology Magazine , 2011,
Abstract: Cytostatic drugs may exert toxic effects on the central nervous system by various mechanisms and may lead to reversible or irreversible neurologic dysfunction. The clinical symptoms are often self-limiting, but may be acute, dramatic, and sometimes even fatal. Since causative therapeutic and even preventive measures are limited, the knowledge of risk factors, characteristic clinical symptoms, symptomatic treatment, and monitoring of the affected patients is essential.
LSST is Not "Big Data"
David Schlegel
Physics , 2012,
Abstract: LSST promises to be the largest optical imaging survey of the sky. If we were fortunate enough to have the equivalent of LSST today, it would represent a "fire hose" of data that would be difficult to store, transfer, and analyze with available compute resources. LSST parallels the SDSS compute task which was ambitious yet tractable. By almost any measure relative to computers that will be available (thanks to the steady progression of Moore's Law), LSST will be a small data set. LSST will never fill more than 22 hard drives. Individual investigators will be able to maintain their own data copies to analyze as they choose.
Model Prediction for the Transverse Single Target-Spin Asymmetry in inclusive DIS
Marc Schlegel
Physics , 2013, DOI: 10.1142/S201019451460012X
Abstract: The single-spin asymmetry of unpolarized leptons scattering deep-inelastically off transversely polarized nucleons is discussed. This observable is generated by a two-photon exchange between lepton and nucleon. In a partonic description of the asymmetry the non-perturbative part is given in terms of multiparton correlations: quark-gluon correlation functions and quark-photon correlation functions. Recently, a model for quark-gluon correlation functions was presented where these objects were expressed through non-valence light cone wave functions. Using this model, estimates for the single-spin asymmetries for a proton and a neutron are presented.
A partonic description of the transverse target single-spin asymmetry in inclusive DIS
Marc Schlegel
Physics , 2012, DOI: 10.1103/PhysRevD.87.034006
Abstract: The single-spin asymmetry of unpolarized leptons scattering deep-inelastically off transversely polarized nucleons is studied in a partonic picture within a collinear twist-3 framework. Since this observable is generated by multi-photon exchanges between lepton and nucleon a partonic description of the asymmetry contains essential elements of a full next-to-leading order calculation for single-spin asymmetries in perturbative Quantum Chromodynamics. In particular it is shown how nontrivial cancellations between kinematical and dynamical twist-3 contributions lead to a well-behaved and finite formula. This final result can be expressed in terms of multipartonic quark-gluon and quark-photon correlation functions. Hence, a measurement of the transverse target single-spin asymmetry may provide new constraints on these multipartonic correlations.
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