4,303 research outputs found
Generalizing Boolean Satisfiability III: Implementation
This is the third of three papers describing ZAP, a satisfiability engine
that substantially generalizes existing tools while retaining the performance
characteristics of modern high-performance solvers. The fundamental idea
underlying ZAP is that many problems passed to such engines contain rich
internal structure that is obscured by the Boolean representation used; our
goal has been to define a representation in which this structure is apparent
and can be exploited to improve computational performance. The first paper
surveyed existing work that (knowingly or not) exploited problem structure to
improve the performance of satisfiability engines, and the second paper showed
that this structure could be understood in terms of groups of permutations
acting on individual clauses in any particular Boolean theory. We conclude the
series by discussing the techniques needed to implement our ideas, and by
reporting on their performance on a variety of problem instances
Subcentimeter Pulmonary Nodules Detected in Patients with Sarcoma
Background. Subcentimeter pulmonary nodules are being detected
with increasing frequency in patients with sarcoma due to the greater use of chest CT,
the advent of helical (spiral) CT scanning and multidetector scanners, and the attendant
decrease in image section thickness.Assessing the clinical significance of these pulmonary
nodules is of particular importance in sarcoma patients, due to the frequent occurrence of
pulmonary metastasis from sarcomas
Superconducting properties of ultrathin Bi2Sr2CaCu2O8+x single crystals
We use Ar-ion milling to thin Bi2212 single crystals down to a few nanometers
or one-to-two (CuO2)2 layers. With decreasing the thickness, superconducting
transition temperature gradually decreases to zero and the in-plane resistivity
increases to large values indicating the existence of a
superconductor-insulator transition in ultrathin Bi2212 single crystals.Comment: 17 pages, 6 figures, to appear in J. Appl. Phys. 98(3) 200
Measurement of stopping beam distributions in the PIBETA detector
Precise calculation of the geometrical acceptance of a large solid angle
detector with an integrated stopping target relies on precise knowledge of the
beam geometry. We describe four alternative methods that we used to measure the
beam stopping distributions in the PIBETA detector active target: (i) light
response of segmented target elements to incident beam particles, (ii)
back-tracking of charged particles from pi+ and mu+ decays using multi-wire
proportional chambers, (iii) volume distribution of the Dalitz decay
(pi0->gamma e+e-) event vertices, and (iv) the opening angle distribution of
two pi0 photons originating from the beta decay of pi+ at rest. We demonstrate
consistent results obtained by these four independent approaches and show how
particular beam stopping distributions affect the detector's geometrical
acceptance.Comment: 38 pages, 16 postscript figures, 2 tables, LaTeX, submitted to Nucl.
Instrum. Meth.
Layered XY-Models, Anyon Superconductors, and Spin-Liquids
The partition function of the double-layer model in the (dual) Villain
form is computed exactly in the limit of weak coupling between layers. Both
layers are found to be locked together through the
Berezinskii-Kosterlitz-Thouless transition, while they become decoupled well
inside the normal phase. These results are recovered in the general case of a
finite number of such layers. When re-interpreted in terms of the dual problems
of lattice anyon superconductivity and of spin-liquids, they also indicate that
the essential nature of the transition into the normal state found in two
dimensions persists in the case of a finite number of weakly coupled layers.Comment: 10 pgs, TeX, LA-UR-94-394
Weakly correlated electrons on a square lattice: a renormalization group theory
We study the weakly interacting Hubbard model on the square lattice using a
one-loop renormalization group approach. The transition temperature T_c between
the metallic and (nearly) ordered states is found. In the parquet regime, (T_c
>> |mu|), the dominant correlations at temperatures below T_c are
antiferromagnetic while in the BCS regime (T_c << |mu|) at T_c the d-wave
singlet pairing susceptibility is most divergent.Comment: 12 pages, REVTEX, 3 figures included, submitted to Phys. Rev. Let
Updating DL-Lite ontologies through first-order queries
In this paper we study instance-level update in DL-LiteA, the description logic underlying the OWL 2 QL standard. In particular we focus on formula-based approaches to ABox insertion and deletion. We show that DL-LiteA, which is well-known for enjoying first-order rewritability of query answering, enjoys a first-order rewritability property also for updates. That is, every update can be reformulated into a set of insertion and deletion instructions computable through a nonrecursive datalog program. Such a program is readily translatable into a first-order query over the ABox considered as a database, and hence into SQL. By exploiting this result, we implement an update component for DLLiteA-based systems and perform some experiments showing that the approach works in practice.Peer ReviewedPostprint (author's final draft
Dynamic Exponent of t-J and t-J-W Model
Drude weight of optical conductivity is calculated at zero temperature by
exact diagonalization for the two-dimensional t-J model with the two-particle
term, . For the ordinary t-J model with =0, the scaling of the Drude
weight for small doping concentration is
obtained, which indicates anomalous dynamic exponent =4 of the Mott
transition. When is switched on, the dynamic exponent recovers its
conventional value =2. This corresponds to an incoherent-to-coherent
transition associated with the switching of the two-particle transfer.Comment: LaTeX, JPSJ-style, 4 pages, 5 eps files, to appear in J. Phys. Soc.
Jpn. vol.67, No.6 (1998
The Anomalous Hall Effect in YBaCuO
The temperature dependence of the normal state Hall effect and
magnetoresistance in YBaCuO is investigated using the Nearly
Antiferromagnetic Fermi Liquid description of planar quasiparticles. We find
that highly anisotropic scattering at different regions of the Fermi surface
gives rise to the measured anomalous temperature dependence of the resistivity
and Hall coefficient while yielding the universal temperature dependence of the
Hall angle observed for both clean and dirty samples. This universality is
shown to arise from the limited momentum transfers available for the anomalous,
spin fluctuation scattering and is preserved for any system with strong
antiferromagnetic correlations.Comment: REVTeX, 10 pages + 4 figures in a single (compressed/uuencoded)
PostScript fil
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