9,399 research outputs found
Modal interpolation program, L215 (INTERP). Volume 1: Engineering and usage
The usage of the Modal Interpolation Program L215 (INTERP) is described. The program uses modal data to form sets of arrays containing interpolation coefficients. The interpolation arrays can then be used to determine displacements at various aerodynamic surface and surface slopes that are parallel and perpendicular to the freestream direction. Five different interpolation methods are available. A description of the data manipulation and the interpolation methods is presented
The Overlap Representation of Skewed Quark and Gluon Distributions
Within the framework of light-cone quantisation we derive the complete and
exact overlap representation of skewed parton distributions for unpolarised and
polarised quarks and gluons. Symmetry properties and phenomenological
applications are discussed.Comment: LaTex, 36 pages. v2: incorrect paper attached originally. v3: erratum
adde
Octet-Baryon Form Factors in the Diquark Model
We present an alternative parameterization of the quark-diquark model of
baryons which particularly takes care of the most recent proton electric
form-factor data from the E136 experiment at SLAC. In addition to
electromagnetic form factors of the nucleon, for which good agreement with data
is achieved, we discuss the weak axial vector form factor of the nucleon as
well as electromagnetic form factors of and hyperons.
Technical advance in calculating the pertinent analytic expressions within
perturbative quantum chromodynamics is gained by formulating the wave function
of the quark-diquark system in a covariant way. Finally, we also comment on the
influence of Sudakov corrections within the scope of the diquark model.Comment: 16 pages, WU-B 93-07, latex, uuencoded postscript files of 7 figures
appended at the end of the latex fil
Quenched charge disorder in CuO2 spin chains: Experimental and numerical studies
We report on measurements of the magnetic response of the anisotropic CuO_2
spin chains in lightly hole-doped La_x (Ca,Sr)_14-x Cu_24 O_41, x>=5. The
experimental data suggest that in magnetic fields B >~ 4T (applied along the
easy axis) the system is characterized by short-range spin order and
quasi-static (quenched) charge disorder. The magnetic susceptibility chi(B)
shows a broad anomaly, which we interpret as the remnant of a spin-flop
transition. To corroborate this idea, we present Monte Carlo simulations of a
classical, anisotropic Heisenberg model with randomly distributed, static
holes. Our numerical results clearly show that the spin-flop transition of the
pure model (without holes) is destroyed and smeared out due to the disorder
introduced by the quasi-static holes. Both the numerically calculated
susceptibility curves chi(B) and the temperature dependence of the position of
the anomaly are in qualitative agreement with the experimental data.Comment: 10 pages, REVTeX4. 11 figures; v2: Fig.2 replaced, small changes in
Figs.1 and 11; minor revisons in Sec. III.C; accepted by Phys. Rev.
The tractability frontier of well-designed SPARQL queries
We study the complexity of query evaluation of SPARQL queries. We focus on
the fundamental fragment of well-designed SPARQL restricted to the AND,
OPTIONAL and UNION operators. Our main result is a structural characterisation
of the classes of well-designed queries that can be evaluated in polynomial
time. In particular, we introduce a new notion of width called domination
width, which relies on the well-known notion of treewidth. We show that, under
some complexity theoretic assumptions, the classes of well-designed queries
that can be evaluated in polynomial time are precisely those of bounded
domination width
Including internal losses in the equivalent circuit model of the SLAC damped detuned structure (DDS)
Exclusive Photoproduction of Large Momentum-Transfer K and K* Mesons
The reactions gamma p -> K+ Lambda and gamma p -> K* Lambda are analyzed
within perturbative QCD, allowing for diquarks as quasi-elementary constituents
of baryons. The diquark-model parameters and the quark-diquark distribution
amplitudes of proton and Lambda are taken from previous investigations of
electromagnetic baryon form factors and Compton-scattering off protons.
Unpolarized differential cross sections and polarization observables are
computed for different choices of the K and K* distribution amplitudes. The
asymptotic form of the K distribution amplitude (proportional to x1 x2) is
found to provide a satisfactory description of the K photoproduction data.Comment: 32 pages, 7 figures available as tared, compressed and uuencoded
PS-file
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Cryptanalysis of Basic Bloom Filters Used for Privacy Preserving Record Linkage
Bloom filter encoded identifiers are increasingly used for privacy preserving record linkage applications, because they allow for errors in encrypted identifiers. However, little research on the security of Bloom filters has been published so far. In this paper, we formalize a successful attack on Bloom filters composed of bigrams. It has previously been assumed in the literature that an attacker knows the global data set from which a sample is drawn. In contrast, we suppose that an attacker does not know this global data set. Instead, we assume the adversary knows a publicly available list of the most frequent attributes. The attack is based on subtle filtering and elementary statistical analysis of encrypted bigrams. The attack described in this paper can be used for the deciphering of a whole database instead of only a small subset of the most frequent names, as in previous research. We illustrate our proposed method with an attack on a database of encrypted surnames. Finally, we describe modifications of the Bloom filters for preventing similar attacks
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