16,258 research outputs found
A representational framework and user-interface for an image understanding workstation
Problems in image understanding involve a wide variety of data (e.g., image arrays, edge maps, 3-D shape models) and processes or algorithms (e.g., convolution, feature extraction, rendering). The underlying structure of an Image Understanding Workstation designed to support mulitple levels and types of representations for both data and processes is described, also the user-interface. The Image Understanding Workstation consists of two parts: the Image Understanding (IU) Framework, and the user-interface. The IU Framework is the set of data and process representations. It includes multiple levels of representation for data such as images (2-D), sketches (2-D), surfaces (2 1/2 D), and models (3-D). The representation scheme for processes characterizes their inputs, outputs, and parameters. Data and processes may reside on different classes of machines. The user-interface to the IU Workstation gives the user convenient access for creating, manipulating, transforming, and displaying image data. The user-interface follows the structure of the IU Framework and gives the user control over multiple types of data and processes. Both the IU Framework and user-interface are implemented on a LISP machine
Supersymmetry of Noncompact MQCD-like Membrane Instantons and Heat Kernel Asymptotics
We perform a heat kernel asymptotics analysis of the nonperturbative
superpotential obtained from wrapping of an M2-brane around a supersymmetric
noncompact three-fold embedded in a (noncompact) G_2-manifold as obtained in
[1], the three-fold being the one relevant to domain walls in Witten's MQCD
[2], in the limit of small "zeta", a complex constant that appears in the
Riemann surfaces relevant to defining the boundary conditions for the domain
wall in MQCD. The MQCD-like configuration is interpretable, for small but
non-zero zeta as a noncompact/"large" open membrane instanton, and for
vanishing zeta, as the type IIA D0-brane (for vanishing M-theory cicle radius).
We find that the eta-function Seeley de-Witt coefficients vanish, and we get a
perfect match between the zeta-function Seeley de-Witt coefficients (up to
terms quadratic in zeta) between the Dirac-type operator and one of the two
Laplace-type operators figuring in the superpotential. This is an extremely
strong signature of residual supersymmetry for the nonperturbative
configurations in M-theory considered in this work.Comment: 21 pages, LaTeX; v3: several clarifying remarks added, to appear in
JHE
Shock-like solutions of the electrostatic Vlasov equation
Shock like solutions of electrostatic Vlasov equatio
Relationship maintenance behavior and adult attachment: an analysis of the actor-partner interdependence model
Associations between relationships maintenance behaviors (positivity, openness, assurances, and sharing tasks) and anxious and avoidant attachment were examined in 265 married couples. Using structural equation modeling to employ the actor-partner interdependence model, the use of positivity, assurances and sharing tasks were found to be negatively associated with anxious and avoidant attachment for both husbands and wives. Being open and self-disclosing in marriage was not strongly associated with attachment. Results indicated that the use of maintenance behaviors in marriages could have the potential to foster increased security in partners. Research and clinical implications are discussed
Magnetic dynamo action in two-dimensional turbulent magneto-hydrodynamics
Two-dimensional magnetohydrodynamic turbulence is explored by means of numerical simulation. Previous analytical theory, based on non-dissipative constants of the motion in a truncated Fourier representation, is verified by following the evolution of highly non-equilibrium initial conditions numerically. Dynamo action (conversion of a significant fraction of turbulent kinetic energy into long-wavelength magnetic field energy) is observed. It is conjectured that in the presence of dissipation and external forcing, a dual cascade will be observed for zero-helicity situations. Energy will cascade to higher wave numbers simultaneously with a cascade of mean square vector potential to lower wave numbers, leading to an omni-directional magnetic energy spectrum which varies as 1/k 3 at lower wave numbers, simultaneously with a buildup of magnetic excitation at the lowest wave number of the system. Equipartition of kinetic and magnetic energies is expected at the highest wave numbers in the system
On toric geometry, Spin(7) manifolds, and type II superstring compactifications
We consider type II superstring compactifications on the singular Spin(7)
manifold constructed as a cone on SU(3)/U(1). Based on a toric realization of
the projective space CP^2, we discuss how the manifold can be viewed as three
intersecting Calabi-Yau conifolds. The geometric transition of the manifold is
then addressed in this setting. The construction is readily extended to higher
dimensions where we speculate on possible higher-dimensional geometric
transitions. Armed with the toric description of the Spin(7) manifold, we
discuss a brane/flux duality in both type II superstring theories compactified
on this manifold.Comment: 14 pages, v2: version to be publishe
Gender and innovation processes in rice-based systems
This GRiSP report is based on the perspectives of women and men from three rice-growing villages in the Nueva Ecija province of the Philippines
A Note on Mirror Symmetry for Manifolds with Spin(7) Holonomy
Starting from the superconformal algebras associated with manifolds, I
extend the algebra to the manifolds with spin(7) holonomy. I show how the
mirror symmetry in manifolds with spin(7) holonomy arises as the automorphism
in the extended sperconformal algebra. The automorphism is realized as 14 kinds
of T-dualities on the supersymmetric toroidal fibrations. One class of
Joyce's orbifolds are pairwise identified under the symmetry.Comment: 12 pages, harvmac bi
Decoherence of spin echoes
We define a quantity, the so-called purity fidelity, which measures the rate
of dynamical irreversibility due to decoherence, observed e.g in echo
experiments, in the presence of an arbitrary small perturbation of the total
(system + environment) Hamiltonian. We derive a linear response formula for the
purity fidelity in terms of integrated time correlation functions of the
perturbation. Our relation predicts, similarly to the case of fidelity decay,
faster decay of purity fidelity the slower decay of time correlations is. In
particular, we find exponential decay in quantum mixing regime and faster,
initially quadratic and later typically gaussian decay in the regime of
non-ergodic, e.g. integrable quantum dynamics. We illustrate our approach by an
analytical calculation and numerical experiments in the Ising spin 1/2 chain
kicked with tilted homogeneous magnetic field where part of the chain is
interpreted as a system under observation and part as an environment.Comment: 22 pages, 10 figure
AGRICULTURAL, FOOD AND HUMAN RESOURCE POLICIES: IMPLICATIONS FOR RURAL AFRICAN-AMERICANS
Agricultural and Food Policy,
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