1,721,010 research outputs found
Practical Algorithms for Multicast Support in Input Queues Switches
No full textThis article is made available under terms and conditions applicable to Open Access Policy Articl
Black hole solutions to the F4-model and their orbits (I)
No full textIn this paper we continue the program of the classification of nilpotent orbits using the approach developed in arXiv:1107.5986, within the study of black hole solutions in D=4 supergravities. Our goal in this work is to classify static, single center black hole solutions to a specific N=2 four-dimensional “magic” model, with special Kähler scalar manifold Sp(6,R)/U(3), as orbits of geodesics on the pseudo-quaternionic manifold F4(4)/[SL(2,R)×Sp′(6,R)] with respect to the action of the isometry group F4(4). Our analysis amounts to the classification of the orbits of the geodesic “velocity” vector with respect to the isotropy group H⁎=SL(2,R)×Sp′(6,R), which include a thorough classification of the nilpotent orbits associated with extremal solutions and reveals a richer structure than the one predicted by the β–γ-labels alone, based on the Kostant–Sekiguchi approach. We provide a general proof of the conjecture made in hep-th/0908.1742 which states that regular single center solutions belong to orbits with coinciding β–γ-labels. We also prove that the reverse is not true by finding distinct orbits with the same β–γ-labels, which are distinguished by suitably devised tensor classifiers. Only one of these is generated by regular solutions. Since regular static solutions only occur with nilpotent degree not exceeding 3, we only discuss representatives of these orbits in terms of black hole solutions. We prove that these representatives can be found in the form of a purely dilatonic four-charge solution (the generating solution in D=3) and this allows us to identify the orbit corresponding to the regular four-dimensional metrics. H⁎-orbits with degree of nilpotency greater than 3 are analyzed solely from a group theoretical point of view, leaving a systematic analysis of their possible interpretation in terms of static multicenter or stationary non-static solutions to a future work. We just limit ourselves to give (singular) single-center representatives of these orbits, to be possibly interpreted as singular limits of regular multicenter solutions. We provide the explicit transformations mapping the various H*-orbits and in particular BPS into non-BPS regular solutions showing that they in general belong to the complexification of the global symmetry group in D=3
NFV Platforms: Taxonomy, Design Choices and Future Challenges
Full text linkDue to the intrinsically inefficient service provisioning in traditional networks, Network Function Virtualization (NFV) keeps gaining attention from both industry and academia. By replacing the purpose-built, expensive, proprietary network equipment with software network functions consolidated on commodity hardware, NFV envisions a shift towards a more agile and open service provisioning paradigm. During the last few years, a large number of NFV platforms have been implemented in production environments that typically face critical challenges, including the development, deployment, and management of Virtual Network Functions (VNFs). Nonetheless, just like any complex system, such platforms commonly consist of abounding software and hardware components and usually incorporate disparate design choices based on distinct motivations or use cases. This broad collection of convoluted alternatives makes it extremely arduous for network operators to make proper choices. Although numerous efforts have been devoted to investigating different aspects of NFV, none of them specifically focused on NFV platforms or attempted to explore their design space. In this paper, we present a comprehensive survey on the NFV platform design. Our study solely targets existing NFV platform implementations. We begin with a top-down architectural view of the standard reference NFV platform and present our taxonomy of existing NFV platforms based on what features they provide in terms of a typical network function life cycle. Then we thoroughly explore the design space and elaborate on the implementation choices each platform opts for. We also envision future challenges for NFV platform design in the incoming 5G era. We believe that our study gives a detailed guideline for network operators or service providers to choose the most appropriate NFV platform based on their respective requirements. Our work also provides guidelines for implementing new NFV platforms
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Staggered HLL: near-continuous-time cardinality estimation with no overhead
No full textMost of existing cardinality estimation algorithms do not support natively interval queries under a sliding window model and are thereby insensitive to data recency. We present Staggered-HyperLogLog (ST-HLL), a probabilistic data structure that takes inspiration from HyperLogLog (HLL) and provides nearly continuous-time estimation of cardinality rates, rather than absolute counts. Our solution has zero-bit overhead with respect to vanilla HLL and negligible additional computational complexity. It is based on a periodic staggered reset of HLL registers and a register equalization operation at query times to compensate for staggered counting. We tested ST-HLL over both synthetic and real Internet traffic traces, showing its ability to track variations of the flow cardinality, quickly adapting to variations under non-stationary flow arrival processes. We show that for the same amount of memory footprint, our algorithm improves the accuracy up to a factor 2x with respect to the state-of-the-art solution, Sliding HLL
Nuclear morphology and ploidy level in infected and uninfected hair root cells of Calluna vulgaris and Vaccinium myrtillus mycorrhizae
No full textPower comparison of cloud data center architectures
No full textPower consumption is a primary concern for cloud computing data centers. Being the network one of the non-negligible contributors to energy consumption in data centers, several architectures have been designed with the goal of improving network performance and energy-efficiency. In this paper, we provide a comparison study of data center architectures, covering both classical two- and three-tier design and state-of-art ones as Jupiter, recently disclosed by Google. Specifically, we analyze the combined effect on the overall system performance of different power consumption profiles for the IT equipment and of different resource allocation policies. Our experiments, performed in small and large scale scenarios, unveil the ability of network-aware allocation policies in loading the the data center in a energy-proportional manner and the robustness of classical two- and three-tier design under network-oblivious allocation strategies
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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