13,642 research outputs found
Simulation of iced wing aerodynamics
The sectional and total aerodynamic load characteristics of moderate aspect ratio wings with and without simulated glaze leading edge ice were studied both computationally, using a three dimensional, compressible Navier-Stokes solver, and experimentally. The wing has an untwisted, untapered planform shape with NACA 0012 airfoil section. The wing has an unswept and swept configuration with aspect ratios of 4.06 and 5.0. Comparisons of computed surface pressures and sectional loads with experimental data for identical configurations are given. The abrupt decrease in stall angle of attack for the wing, as a result of the leading edge ice formation, was demonstrated numerically and experimentally
Relating U(N)xU(N) to SU(N)xSU(N) Chern-Simons Membrane theories
By integrating out the U(1)_B gauge field, we show that the U(n)xU(n) ABJM
theory at level k is equivalent to a Z_k identification of the
(SU(n)xSU(n))/Z_n Chern-Simons theory, but only when n and k are coprime. As a
consequence, the k=1 ABJM model for two M2-branes in R^8 can be identified with
the N=8 (SU(2)xSU(2))/Z_2 theory. We also conjecture that the U(2)xU(2) ABJM
model at k=2 is equivalent to the N=8 SU(2)xSU(2)-theory.Comment: 16 pages, Latex; v2: references added; v3: Clarifications adde
Work distribution for the driven harmonic oscillator with time-dependent strength: Exact solution and slow driving
We study the work distribution of a single particle moving in a harmonic
oscillator with time-dependent strength. This simple system has a non-Gaussian
work distribution with exponential tails. The time evolution of the
corresponding moment generating function is given by two coupled ordinary
differential equations that are solved numerically. Based on this result we
study the behavior of the work distribution in the limit of slow but finite
driving and show that it approaches a Gaussian distribution arbitrarily well
Body composition of male office workers compared by means of infrared reflection measurement, bioimpedance analysis and calipermetry
There are currently many different anthropometric methods to determine individual body fat percentage, as well as almost as many variants of bioelectric impedance analysis (BIA) and only a single method of infrared reflection measurement (IR) as easily feasible methods of field research. The present study aims at a simultaneous comparison between calipermetry, IR and BIA. In particular, the question which measurement method could be used as an equivalent method in the event of failure of the BIA or IR is investigated. The sample group consisted of 250 male office workers from the Rhine-Main area (average age 31.75 ± 9.16 years, average height 178.5 ± 6.93 cm and average weight 80.61 ± 9.42 kg). The measurements were previously scheduled and mostly carried out during the lunch break. For anthropometry, 13 skin fat folds were measured with the help of the Accu® Measure Caliper, thigh circumference with the help of a measuring tape, height with a height measuring device and body mass on the weight scale. Subsequently, an IR measurement (Futrex®) and a BIA (InBody®) were performed on the same subject. The parameters of body fat percentage and total body water (in litres) were examined. The statistical methods were correlation coefficients, Bland-Altman comparison and paired t-test for equivalence. For the men studied, the highest correlation coefficients were in the comparisons between the formulas according to Parízkova & Buzkova 1 and Parízkova & Buzkova 3 (r = 0.93), as well as for Parízkova & Buzkova 3 and Parízkova & Buzkova 4 (r = 0.96). The correlation coefficient for the IR vs. BIA comparison was only r = 0.56. A key result of the present study was the finding that certain methods cannot be substituted in an equivalent way, in fact only some calipermetric regression equations
Interaction between M2-branes and Bulk Form Fields
We construct the interaction terms between the world-volume fields of
multiple M2-branes and the 3- and 6-form fields in the context of ABJM theory
with U()U() gauge symmetry. A consistency check is made in the
simplest case of a single M2-brane, i.e, our construction matches the known
effective action of M2-brane coupled to antisymmetric 3-form field. We show
that when dimensionally reduced, our couplings coincide with the effective
action of D2-branes coupled to R-R 3- and 5-form fields in type IIA string
theory. We also comment on the relation between a coupling with a specific
6-form field configuration and the supersymmetry preserving mass deformation in
ABJM theory.Comment: 30 pages, version to appear in JHE
M-Theory in the Gaugeon Formalism
In this paper we will analyse the Aharony-Bergman-Jafferis-Maldacena (ABJM)
theory in superspace formalism. We then study the quantum gauge
transformations for this ABJM theory in gaugeon formalism. We will also analyse
the extended BRST symmetry for this ABJM theory in gaugeon formalism and show
that these BRST transformations for this theory are nilpotent and this in turn
leads to the unitary evolution of the -matrix.Comment: 8 pages, 0 figures, accepted for publication in Comm. Theor. Phy
New and old N=8 superconformal field theories in three dimensions
We show that an infinite family of N=6 d=3 superconformal Chern-Simons-matter
theories has hidden N=8 superconformal symmetry and hidden parity on the
quantum level. This family of theories is different from the one found by
Aharony, Bergman, Jafferis and Maldacena, as well as from the theories
constructed by Bagger and Lambert, and Gustavsson. We also test several
conjectural dualities between BLG theories and ABJ theories by comparing
superconformal indices of these theories.Comment: 16 pages, late
4D visualization of embryonic, structural crystallization by single-pulse microscopy
In many physical and biological systems the transition from an amorphous to ordered native structure involves complex energy landscapes, and understanding such transformations requires not only their thermodynamics but also the structural dynamics during the process. Here, we extend our 4D visualization method with electron imaging to include the study of irreversible processes with a single pulse in the same ultrafast electron microscope (UEM) as used before in the single-electron mode for the study of reversible processes. With this augmentation, we report on the transformation of amorphous to crystalline structure with silicon as an example. A single heating pulse was used to initiate crystallization from the amorphous phase while a single packet of electrons imaged selectively in space the transformation as the structure continuously changes with time. From the evolution of crystallinity in real time and the changes in morphology, for nanosecond and femtosecond pulse heating, we describe two types of processes, one that occurs at early time and involves a nondiffusive motion and another that takes place on a longer time scale. Similar mechanisms of two distinct time scales may perhaps be important in biomolecular folding
Index for Three Dimensional Superconformal Field Theories and Its Applications
We review aspects of superconformal indices in three dimension. Three
dimensional superconformal indices can be exactly computed by using
localization method including monopole contribution, and can be applied to
provide evidences for mirror duality, AdS_4/CFT_3 correspondence and global
symmetry enhancement of strongly coupled gauge theories. After reviewing, we
discuss the possibility of global symmetry enhancement in a finite rank of
gauge group.Comment: 14 pages, Proceedings of the Seventh International Conference Quantum
Theory and Symmetries (QTS-7) in Prague, Czech Republic, August, 2011; v2:
minor modifications, discussion of supersymmetry enhancement of abelian ABJM
theory by using an index were adde
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