19,387 research outputs found
Exact polarizability and plasmon resonances of partly buried nanowires
The electrostatic polarizability for both vertical and horizontal
polarization of two conjoined half-cylinders partly buried in a substrate is
derived in an analytical closed-form expression. Using the derived analytical
polarizabilities we analyze the localized surface plasmon resonances of three
important metal nanowire configurations: (1) a half-cylinder, (2) a
half-cylinder on a substrate, and (3) a cylinder partly buried in a substrate.
Among other results we show that the substrate plays an important role for
spectral location of the plasmon resonances. Our analytical results enable an
easy, fast, and exact analysis of many complicated plasmonic nanowire
configurations including nanowires on substrates. This is important both for
comparison with experimental data, for applications, and as benchmarks for
numerical methods
Is there a non-Standard-Model contribution in non-leptonic b -> s decays?
Precision measurements of branching fractions and CP asymmetries in
non-leptonic b -> s decays reveal certain "puzzles" when compared with Standard
Model expectations based on a global fit of the CKM triangle and general
theoretical expectations. Without reference to a particular model, we
investigate to what extent the (small) discrepancies observed in (B -> J/psi
K), (B -> phi K) and (B -> K pi) may constrain new physics in (b -> s q qbar)
operators. In particular, we compare on a quantitative level the relative
impact of different quark flavours q=c,s,u,d.Comment: 25 pages, 7 figures, some references added, brief discussion of B ->
J/psi \pi include
CRiBAC: Community-centric role interaction based access control model
As one of the most efficient solutions to complex and large-scale problems, multi-agent cooperation has been in the limelight for the past few decades. Recently, many research projects have focused on context-aware cooperation to dynamically provide complex services. As cooperation in the multi-agent systems (MASs) becomes more common, guaranteeing the security of such cooperation takes on even greater importance. However, existing security models do not reflect the agents' unique features, including cooperation and context-awareness. In this paper, we propose a Community-based Role interaction-based Access Control model (CRiBAC) to allow secure cooperation in MASs. To do this, we refine and extend our preliminary RiBAC model, which was proposed earlier to support secure interactions among agents, by introducing a new concept of interaction permission, and then extend it to CRiBAC to support community-based cooperation among agents. We analyze potential problems related to interaction permissions and propose two approaches to address them. We also propose an administration model to facilitate administration of CRiBAC policies. Finally, we present the implementation of a prototype system based on a sample scenario to assess the proposed work and show its feasibility. © 2012 Elsevier Ltd. All rights reserved
General Analysis of U-Spin Breaking in B Decays
We analyse the breaking of U-spin on a group theoretical basis. Due to the
simple behaviour of the weak effective hamiltonian under U-spin and the unique
structure of the breaking terms such a group theoretical analysis leads to a
manageable number of parameters. Several applications are discussed, including
the decays B -> J/psi K and B -> D K.Comment: 18 pages, 2 figures; Paragraph added on decays of B0 to P+P- with
P=(pi,K), and several minor corrections performed. Version matches the one to
appear in Phys. Rev.
Sparse Signal Processing Concepts for Efficient 5G System Design
As it becomes increasingly apparent that 4G will not be able to meet the
emerging demands of future mobile communication systems, the question what
could make up a 5G system, what are the crucial challenges and what are the key
drivers is part of intensive, ongoing discussions. Partly due to the advent of
compressive sensing, methods that can optimally exploit sparsity in signals
have received tremendous attention in recent years. In this paper we will
describe a variety of scenarios in which signal sparsity arises naturally in 5G
wireless systems. Signal sparsity and the associated rich collection of tools
and algorithms will thus be a viable source for innovation in 5G wireless
system design. We will discribe applications of this sparse signal processing
paradigm in MIMO random access, cloud radio access networks, compressive
channel-source network coding, and embedded security. We will also emphasize
important open problem that may arise in 5G system design, for which sparsity
will potentially play a key role in their solution.Comment: 18 pages, 5 figures, accepted for publication in IEEE Acces
Confined Multilamellae Prefer Cylindrical Morphology
By evaporating a drop of lipid dispersion we generate the myelin morphology
often seen in dissolving surfactant powders. We explain these puzzling
nonequilibrium structures using a geometric argument: The bilayer repeat
spacing increases and thus the repulsion between bilayers decreases when a
multilamellar disk is converted into a myelin without gain or loss of material
and with number of bilayers unchanged. Sufficient reduction in bilayer
repulsion can compensate for the cost in curvature energy, leading to a net
stability of the myelin structure. A numerical estimate predicts the degree of
dehydration required to favor myelin structures over flat lamellae.Comment: 6 pages, 3 figures, submitted to Euro. Phys. J.
Die Unfähigkeit zu lachen : die permanente Wiedergeburt des Führers aus dem Geist der Unterhaltung
Tourism in Metropolitan Manila - Philippines: An Analysis
Tourism has become important for (mega)cities in Southeast Asia. Metropolitan Manila competes in the tourism market, but its tourism is scholarly unexplored so far. This Ph.D. thesis takes the approach, that urban tourism is a system comprising interacting stakeholders at the supply and consumer side, and visitor attractions. This dissertation analyses and characterizes Metropolitan Manila`s tourism system referring to its stakeholders, visitor attractions and services. Metropolitan Manila is able to tap the domestic and international tourism market with various attraction resources. But Metropolitan Manila`s supply-side stakeholder field appears highly diverse. The relations among these stakeholders can be characterized through discontinuous links, unequal participation, and non power-sharing. This adverse status is aggravated through the absence of tourism policy, obsolete tourism planning approaches and the dominance of top-down deciding political elites. Consequently, a consensual, goal-oriented acting is inhibited. Instead stakeholders act mutually exclusive or compete with each other. Tourism is predominately seen as a valuable economic tool. As a result, other important dimensions of tourism like socio-cultural, experiential, and infrastructural aspects are negated to a great extent. The current visitor is a short staying stop-over traveller who recognizes the capital`s built heritage as unique. Visitor activities and spatial flow are mainly confined on the heritage of the city centre. But the visitor`s impression of the capital is negative and dissatisfaction with public sector services occurs. Valuable visitor attractions are difficult to access and the tourism infrastructure is perceived as weakly developed. This emphasizes that the tourism officials are not able to create a fully convincing tourism product and they neglect other metropolitan-wide tourism potentials. Recommended future measures should improve the cooperation of supply-side stakeholders and tourism planning embracing the whole metropolis. Moreover, measures must improve tourism infrastructure, public sector services, marketing, and destination image of the capital in order to enhance its competitiveness
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