17,260 research outputs found
A method for determining the preferred orientation of crystallites normal to a surface
Techniques representing the angular distribution of a particular direction in a crystallographic reference frame or analytical methods were developed. The data required by these techniques for displaying preferred orientation is obtained by measuring the orientation of a large number of crystallites. This may be done visually using etch-pit or Laue techniques which, experimentally, are both tedious and difficult. The intensities of X ray diffraction maxima are proportional to the number of crystallites whose crystallographic plane normals bisect the incident and diffracted beams. Parameters used in calculating powder patterns are also presented
Quantum Entangled Dark Solitons Formed by Ultracold Atoms in Optical Lattices
Inspired by experiments on Bose-Einstein condensates in optical lattices, we
study the quantum evolution of dark soliton initial conditions in the context
of the Bose-Hubbard Hamiltonian. An extensive set of quantum measures is
utilized in our analysis, including von Neumann and generalized quantum
entropies, quantum depletion, and the pair correlation function. We find that
quantum effects cause the soliton to fill in. Moreover, soliton-soliton
collisions become inelastic, in strong contrast to the predictions of
mean-field theory. These features show that the lifetime and collision
properties of dark solitons in optical lattices provide clear signals of
quantum effects.Comment: 4 pages, 4 figures; version appearing in PRL, only minor changes from
v
Estimating the Knowledge-Capital Model of the Multinational Enterprise
What we term the firm includes three principal assumptions. First, services of knowledge-based and knowledge-generating activities, such as R&D, can be geographically separated from production and supplied to production facilities at low cost. Second, these knowledge-intensive activities are skilled-labor intensive relative to production. These characteristics give rise to vertical multinationals, which fragment production and locate activities according to factor prices and market size. Third, knowledge-based services have a (partial) joint-input characteristic that they can be supplied to additional production facilities at low cost. This characteristic gives rise to horizontal multinationals, which produce the same goods or services in multiple locations. In this paper, we note how this model predicts relationships between affiliate sales and country characteristics. We then subject these predictions to empirical tests.
Proceedings of the MECA Workshop on The Evoluation of the Martian Atmosphere
Topics addressed include: Mars' volatile budget; climatic implications of martian channels; bulk composition of Mars; accreted water inventory; evolution of CO2; dust storms; nonlinear frost albedo feedback on Mars; martian atmospheric evolution; effects of asteroidal and cometary impacts; and water exchange between the regolith and the atmosphere/cap system over obliquity timescales
Dynamic behavior of an unsteady trubulent boundary layer
Experiments on an unsteady turbulent boundary layer are reported in which the upstream portion of the flow is steady (in the mean) and in the downstream region, the boundary layer sees a linearly decreasing free stream velocity. This velocity gradient oscillates in time, at frequencies ranging from zero to approximately the bursting frequency. For the small amplitude, the mean velocity and mean turbulence intensity profiles are unaffected by the oscillations. The amplitude of the periodic velocity component, although as much as 70% greater than that in the free stream for very low frequencies, becomes equal to that in the free stream at higher frequencies. At high frequencies, both the boundary layer thickness and the Reynolds stress distribution across the boundary layer become frozen. The behavior at higher amplitude is quite similar. At sufficiently high frequencies, the boundary layer thickness remains frozen at the mean value over the oscillation cycle, even though flow reverses near the wall during a part of the cycle
Bose-Einstein Condensates in Rotating Lattices
Strongly interacting bosons in 2D in a rotating square lattice are
investigated via a modified Bose-Hubbard Hamiltonian. Such a system corresponds
to a rotating lattice potential imprinted on a trapped Bose-Einstein
condensate. Second-order quantum phase transitions between states of different
symmetries are observed at discrete rotation rates. For the square lattice we
study, there are four possible ground-state symmetries.Comment: 4 pages, 5 figures, Accepted for publication in PRL v2: Replaced
phase winding labels with symmetry eigenstate indices, replaced Gaussian
Ansatz with more general treatment and other minor change
Using Semantic Web Technologies to Support Enhanced Situation Awareness
The AKTiveSA project is using Semantic Web technologies to support information fusion and enhanced situational awareness in a simulated humanitarian relief scenario. We have developed an application that shows how situational awareness can be supported during humanitarian relief situations; often occurring alongside military conflict. Semantic Web technologies provide new opportunities for harvesting information from numerous, disparate and often heterogeneous information sources and can be used to better support complex knowledge fusion
Recommended from our members
An atlas of CO2 storage potential in the nearshore waters of the Texas coast ā American Recovery and Reinvestment Act ā āGulf of Mexico Miocene CO2 site characterization mega-transectā
Bureau of Economic Geolog
- ā¦