1,953 research outputs found
Chemical-potential flow equations for graphene with Coulomb interactions
We calculate the chemical potential dependence of the renormalized Fermi
velocity and static dielectric function for Dirac quasiparticles in graphene
nonperturbatively at finite temperature. By reinterpreting the chemical
potential as a flow parameter in the spirit of the functional renormalization
group (fRG) we obtain a set of flow equations, which describe the change of
these functions upon varying the chemical potential. In contrast to the fRG the
initial condition of the flow is nontrivial and has to be calculated
separately. Our results confirm that the charge carrier density dependence of
the Fermi velocity is negligible, validating the comparison of the fRG
calculation at zero density of Bauer et al., Phys. Rev. B 92, 121409 (2015)
with the experiment of Elias et al., Nat. Phys. 7, 701 (2011).Comment: 7 pages, 4 figure
Broadband cloaking with volumetric structures composed of two-dimensional transmission-line networks
The cloaking performance of two microwave cloaks, both based on the recently
proposed transmission-line approach, are studied using commercial full-wave
simulation software. The cloaks are shown to be able to reduce the total
scattering cross sections of metallic objects of some restricted shapes and
sizes. One of the studied cloaks is electrically small in diameter, and the
other is electrically large, with the diameter equal to several wavelengths.Comment: 6 pages, 7 figure
The Success of Motion Pictures
THE SUCCESS OF MOTION PICTURES â AN ECONOMIC GAMBLE: SELECTED MOVIE EXPLOITATION PHENOMENA More than 5,000 marketable movies are produced worldwide every year - a risky economic gamble running into billions. Despite the potential risk of commercial failure, film producers still try to achieve outstanding box-office results. There are also special movies that are able to preserve or even increase their intrinsic value due to the longevity of their commercial success. This article focuses on distinctive movie exploitation phenomena, which can be observed worldwide. These phenomena show the unpredictability of film success due to the fact that the cycles, the duration, and the progress of film exploitation are unforeseeable. MythSuccess is the big myth of the international film industry: on the one hand enormous profits, glamour, film stars, red carpet shows at Cannes, Berlin, and Venice - the big film festivals. And as climax - the Oscars in..
Event-based analysis: Identifying and sequencing prehistoric activities in buried palimpsests. An example from Lake George, Australia.
This thesis presents a new methodology for sequencing behavioural events in sub-surface stone artefact assemblages. While methods have been previously presented for the identification of activities, often termed 'moments in time', these studies have focused on temporally bounded living floors, usually in cave environments. Buried assemblages in open landscapes often do not retain such coherence, and so the development of a methodology for identifying and sequencing behavioural events in mixed assemblages is needed. This study develops a method, here termed event-based analysis (EBA), for the temporal sequencing of discrete activities in undifferentiated stratigraphies with vertically distributed artefactual deposits, which then allows comparisons of prehistoric activities to be made across space and time. Event-based analysis draws on several methods previously presented in the literature, principally RMU analysis, life-history framework and refitting for the reunification of refuse from single stone-working activities and the construction of inferences regarding the reduction and flow of stone though a site. Event-based analysis relies on these methods for identifying and understanding discrete stone working activities. EBA then extends the applicability of these methods to the analysis of temporally deep buried assemblages by providing a method whereby identified knapping and discard events can be sequenced. This shifts the unit of analysis in buried palimpsests from the assemblage to the event, and allows comparisons to be built over time and space from this behaviourally meaningful unit. This thesis is concerned with how archaeologists make inferences about prehistoric cultures from the archaeological record. To this end, a new methodological framework, event-based analysis, is advanced which both guides the construction of evidence-led inferences regarding prehistoric behaviour, and promotes the comparison of those behavioural inferences for the purpose of producing generalisations concerning use of place (Schiffer 2011). Using EBA, this project examines the configuration of foraging economies and technologies in the Lake George area of south-eastern Australia. A detailed place-use history is built from the comparison of discrete knapping and discard events over time and space. This thesis thus contributes to the development of archaeological methodologies which seek to build detailed and meaningful âthick descriptionsâ (sensu Geertz (1973)) which are firmly grounded in the evidence examined. The aim is to provide detailed descriptions of the human activities which produced the stone artefact assemblages; it is to elucidate the âdelicacy of its distinctions, not the sweep of its abstractionsâ (Geertz 1973:25)
Integral equation mei applied to three-dimensional arbitrary surfaces
The authors present a new formulation of the integral equation of the measured equation of invariance (MEI) as a confined field integral equation discretised by the method of moments, in which the use of numerically derived testing functions results in an approximately sparse linear system with storage memory requirements and a CPU time for computing the matrix coefficients proportional to the number of unknowns.Peer ReviewedPostprint (published version
Spatial Multiplexing of QPSK Signals with a Single Radio: Antenna Design and Over-the-Air Experiments
The paper describes the implementation and performance analysis of the first
fully-operational beam-space MIMO antenna for the spatial multiplexing of two
QPSK streams. The antenna is composed of a planar three-port radiator with two
varactor diodes terminating the passive ports. Pattern reconfiguration is used
to encode the MIMO information onto orthogonal virtual basis patterns in the
far-field. A measurement campaign was conducted to compare the performance of
the beam-space MIMO system with a conventional 2-by-?2 MIMO system under
realistic propagation conditions. Propagation measurements were conducted for
both systems and the mutual information and symbol error rates were estimated
from Monte-Carlo simulations over the measured channel matrices. The results
show the beam-space MIMO system and the conventional MIMO system exhibit
similar finite-constellation capacity and error performance in NLOS scenarios
when there is sufficient scattering in the channel. In comparison, in LOS
channels, the capacity performance is observed to depend on the relative
polarization of the receiving antennas.Comment: 31 pages, 23 figure
Analysis of microstrip antennas by multilevel matrix decomposition algorithm
Integral equation methods (IE) are widely used in conjunction with Method of Moments (MoM) discretization for the numerical analysis of microstrip antennas. However, their application to large antenna arrays is difficult due to the fact that the computational requirements increase rapidly with the number of unknowns N. Several techniques have been proposed to reduce the computational cost of IE-MoM. The Multilevel Matrix Decomposition Algorithm (MLMDA) has been implemented in 3D for arbitrary perfectly conducting surfaces discretized in Rao, Wilton and Glisson linear triangle
basis functions . This algorithm requires an operation count that is proportional to N·log2N. The performance of the algorithm is much better for planar or piece-wise planar objects than for general 3D problems, which makes the algorithm particularly well-suited for the analysis of microstrip antennas. The memory requirements are proportional to N·logN and very low. The main advantage of the MLMDA compared with other efficient techniques to solve integral equations is that it does not rely on specific mathematical properties of the Green's functions being used. Thus, we can apply the method to interesting configurations governed by special Green's functions like multilayered media. In fact, the MDA-MLMDA method can
be used at the top of any existing MoM code. In this paper we present the application to the analysis of large printed antenna arrays.Peer ReviewedPostprint (published version
Green's functions in layered media: Imaginary axis integration and asymptotic behavior
This paper presents an efficient technique for evaluating Greenâs functions associated to layered media, when cast in the space domain as Sommerfeld integrals. The theoretical developments needed to set up the numerical algorithm throw a new light on the asymptotic behavior of these Greenâs functions for large transverse source-observer distances.The authors wish to thank Rich Hall from Boulder Microwave Technologies Inc.and Yan Brand from Ecole Polytechnique Fkdkrale de Lausanne for helpful discussion and advice
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