5,614 research outputs found
Characterisation and textural analysis of Middle Bronze Age Transdanubian inlaid wares of the Encrusted Pottery Culture, Hungary: a preliminary study
Inlaid ceramics belonging to the Encrusted Pottery Culture and dated to the Middle Bronze Age (2000–1500 BC) are highly distinctive vessels with complex decorative motifs found in large numbers in the Transdanubia region of Hungary. Despite this considerable corpus of material there has been little systematic investigation of the composition of the inlays. Micro-analysis of Transdanubian inlaid wares by X-ray diffraction (XRD), micro-Fourier transform infrared microscopy (FT-IR), and scanning electron microscopy (SEM) provides new compositional, structural and textural information on the inlays. In contrast to common statements in the literature regarding the materials used to make inlays, these new data show that the majority of inlays are composed of hydroxyapatite (bone) that was previously ashed, although some of the inlays are composed of calcium carbonate. Additional compositional and textural variation in the bone inlays suggests that bone material from different skeletal elements and/or of different age may have been used, and that contrasting recipes for inlay preparation were employed during fabrication. These results suggest that the production of inlaid vessels of the Encrusted Pottery Culture was more complex than has hitherto been thought
Optimized quantum random-walk search algorithms
Shenvi, Kempe and Whaley's quantum random-walk search (SKW) algorithm [Phys.
Rev. A 67, 052307 (2003)] is known to require number of oracle
queries to find the marked element, where is the size of the search space.
The overall time complexity of the SKW algorithm differs from the best
achievable on a quantum computer only by a constant factor. We present
improvements to the SKW algorithm which yield significant increase in success
probability, and an improvement on query complexity such that the theoretical
limit of a search algorithm succeeding with probability close to one is
reached. We point out which improvement can be applied if there is more than
one marked element to find.Comment: 7 pages, 2 figures. Major revision according to referee repor
Giant magnetoresistance (GMR) in electrodeposited multilayer films: the influence of superparamagnetic regions
When preparing an alternating sequence of magnetic (Co or Ni) and non-magnetic (Cu)
layers by electrodeposition using the two-pulse plating technique, a dissolution of the lessnoble
magnetic Co and Ni atoms can take place during the deposition of the more noble and
non-magnetic Cu atoms. This process results in changes of the actual sublayer thicknesses
with respect to the nominal values and can also cause some chemical intermixing at the
magnetic/non-magnetic interfaces. As a consequence, superparamagnetic (SPM) regions
with “loose magnetic moments” can form as has been demonstrated for electrodeposited
Ni-Cu/Cu multilayers. We have also shown recently for electrodeposited Co-Cu/Cu
multilayers that if some fraction of the magnetic layers exhibits SPM behaviour then the
observed giant magnetoresistance (GMR) can be quantitatively decomposed into a
ferromagnetic (FM) and a SPM contribution. In this paper, the results of a similar GMR
decomposition study are presented for two electrodeposited Co-Cu/Cu multilayers. In the
multilayer with strongly non-saturated magnetoresistance curves, the dominant GMR term
was due to SPM regions, whereas in the other multilayer for which the magnetoresistance is
mostly saturated in magnetic fields around 1 to 2 kOe, the FM contribution to the GMR is
much larger. At the same time, magnetic measurements on the first multilayer sample have
also revealed the presence of a large SPM contribution to the magnetization
Rapid convergence of time-averaged frequency in phase synchronized systems
Numerical and experimental evidence is presented to show that many phase
synchronized systems of non-identical chaotic oscillators, where the chaotic
state is reached through a period-doubling cascade, show rapid convergence of
the time-averaged frequency. The speed of convergence toward the natural
frequency scales as the inverse of the measurement period. The results also
suggest an explanation for why such chaotic oscillators can be phase
synchronized.Comment: 6 pages, 9 figure
Improving Link Reliability through Network Coding in Cooperative Cellular Networks
The paper proposes a XOR-based network coded cooperation protocol for the uplink transmission of relay assisted cellular networks and an algorithm for selection and assignment of the relay nodes. The performances of the cooperation protocol are expressed in terms of network decoder outage probability and Block Error Rate of the cooperating users. These performance indicators are analyzed theoretically and by computer simulations. The relay nodes assignment is based on the optimization, according to several criteria, of the graph that describes the cooperation cluster formed after an initial selection of the relay nodes. The graph optimization is performed using Genetic Algorithms adapted to the topology of the cooperation cluster and the optimization criteria considered
Dense cores in the dark cloud complex LDN1188
We present a molecular line emission study of the LDN1188 dark cloud complex
located in Cepheus. In this work we focused on the densest parts of the cloud
and on the close neighbourhood of infrared point sources. We made ammonia
mapping with the Effelsberg 100-m radio telescope and identified 3 dense cores.
CS(1--0), CS(2--1) and HCO(1--0) measurements performed with the Onsala
20\,m telescope revealed the distribution of dense molecular material. The
molecular line measurements were supplemented by mapping the dust emission at
1.2\,mm in some selected directions using the IRAM 30\,m telescope. With these
data we could work out a likely evolutionary sequence in this dark clould
complex.Comment: YouResAstro2012 conference presentation; accepted to Astronomishen
Nachrichten (25-July-2013
Simulating Business Processes of Manufacturing SMEs on the Cloud
Simulating the efficiency of business processes could reveal crucial bottlenecks for manufacturing companies and could lead to significant optimizations resulting in decreased time to market, more efficient resource utilization, and larger profit. While such business optimization software is widely utilized by larger companies, SMEs typically do not have the required expertise and resources to efficiently exploit these advantages. The aim of this work is to explore how simulation software vendors and consultancies can extend their portfolio to SMEs by providing business process optimization based on a cloud computing platform. By executing simulation runs on the cloud, software vendors and associated business consultancies can get access to large computing power and data storage capacity on demand, run large simulation scenarios on behalf of their clients, analyze simulation results, and advise their clients regarding process optimization. The solution is mutually beneficial for both vendor/consultant and the end-user SME. End-user companies will only pay for the service without requiring large upfront costs for software licenses and expensive hardware. Software vendors can extend their business towards the SME market with potentially huge benefits
Pushing the limits, episode 2: K2 observations of extragalactic RR Lyrae stars in the dwarf galaxy Leo IV
We present the first observations of extragalactic pulsating stars in the K2
ecliptic survey of the Kepler space telescope. Variability of all three RR
Lyrae stars in the dwarf spheroidal galaxy Leo IV were successfully detected,
at a brightness of Kp~21.5 mag, from data collected during Campaign 1. We
identified one modulated star and another likely Blazhko candidate with periods
of 29.8+-0.9 d and more than 80 d, respectively. EPIC 210282473 represents the
first star beyond the Magellanic Clouds for which the Blazhko period and
cycle-to-cycle variations in the modulation were unambiguously measured.The
photometric [Fe/H] indices of the stars agree with earlier results that Leo IV
is a very metal-poor galaxy. Two out of three stars blend with brighter
background galaxies in the K2 frames. We demonstrate that image subtraction can
be reliably used to extract photometry from faint confused sources that will be
crucial not only for the K2 mission but for future space photometric missions
as well.Comment: 8 pages, 6 figures, accepted for publication in the Astrophysical
Journal. Light curves can be downloaded from http://konkoly.hu/KIK/data.htm
Fermi Surface Nesting and the Origin of the Charge Density Wave in NbSe
We use highly accurate density functional calculations to study the band
structure and Fermi surfaces of NbSe2. We calculate the real part of the
non-interacting susceptibility, Re chi_0(q), which is the relevant quantity for
a charge density wave (CDW) instability and the imaginary part, Im chi_0(q),
which directly shows Fermi surface (FS) nesting. We show that there are very
weak peaks in Re chi_0(q) near the CDW wave vector, but that no such peaks are
visible in Im chi_0(q), definitively eliminating FS nesting as a factor in CDW
formation. Because the peak in Re chi_0(q) is broad and shallow, it is unlikely
to be the direct cause of the CDW instability. We briefly address the
possibility that electron-electron interactions (local field effects) produce
additional structure in the total (renormalized) susceptibility, and we discuss
the role of electron-ion matrix elements.Comment: Replacement of Table II values, minor changes to tex
N=4 central charge superspace at work for supergravity coupled to an arbitrary number of abelian vector multiplets
We present the description in central charge superspace of N=4 supergravity
with antisymmetric tensor coupled to an arbitrary number of abelian vector
multiplets. All the gauge vectors of the coupled system are treated on the same
footing as gauge fields corresponding to translations along additional bosonic
coordinates. It is the geometry of the antisymmetric tensor which singles out
which combinations of these vectors belong to the supergravity multiplet and
which are the additional coupled ones. Moreover, basic properties of
Chapline-Manton coupling mechanism, as well as the SO(6,n)/SO(6)*SO(n) sigma
model of the Yang-Mills scalars are found as arising from superspace geometry.Comment: 18 page
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