118,529 research outputs found
Application of numerical optimization to the design of wings with specified pressure distributions
A practical procedure for the optimum design of transonic wings is demonstrated. The procedure uses an optimization program based on the method of feasible directions coupled with an aerodynamic analysis program which solves the three-dimensional potential equation for subsonic through transonic flow. Two new wings for the A-7 aircraft were designed by using the optimization procedure to achieve specified surface pressure distributions. The new wings, along with the existing A-7 wing, were tested in the Ames 11 ft transonic wind tunnel. The experimental data show that all of the performance goals were met. However, comparisons of the wind tunnel results with the theoretical predictions indicate some differences at conditions for which strong shock waves occur
Optically controlled spin-glasses in multi-qubit cavity systems
Recent advances in nanostructure fabrication and optical control, suggest
that it will soon be possible to prepare collections of interacting two-level
systems (i.e. qubits) within an optical cavity. Here we show theoretically that
such systems could exhibit novel phase transition phenomena involving
spin-glass phases. By contrast with traditional realizations using magnetic
solids, these phase transition phenomena are associated with both matter and
radiation subsystems. Moreover the various phase transitions should be tunable
simply by varying the matter-radiation coupling strength.Comment: 4 pages, 3 figure
Saline Conversion and Ice Structures from Artificially Grown Sea Ice
The environment of cold regions is generally viewed as inhospitable, primarily
due to application of ideal processes and techniques suitable to temperate
zones. The work herein is a step toward solving two environmental problems.
The first involves the supply of inexpensive, potable water in Arctic regions,
the lack of which is a severe detriment to development. Although water does
exist in the Arctic, it is neither available in potable form during many months
of the year nor does it occur in sufficient quantity near the point of use. Principally,
this lack is caused by the aridness of the Arctic and the shallowness
of fresh water sources which, for all practical purposes, do not exist but
freeze completely each winter season. The remaining liquid water source is
the sea. Arctic problems are then similar to other arid regions where the
conversion of sea water to potable water or the transmission of potable water
to desired locations is necessary. Cold temperatures generally preclude
transmission except over very short distances.
Desalination by freezing sea water is a much reported process and has been
included among the desalination processes under study worldwide. The
advantage of this method in the Arctic is the cold winter-time temperature
for freezing and the existence of adequate solar energy in the summer for
melting self purified ice. Power requirements are greatly reduced using these
natural phenomena.
The second aspect of this study concerns the use of artificially grown sea ice
as a structural material, thinking primarily in terms of coastal facilities such
as docks, jetties, islands, platforms, etc. At sufficiently high latitudes, the
summer ablation can be controlled to the point where major structures can be
maintained intact during the summer. The unit cost of material is quite low
because of low energy requirements.
The results of this study show that each of these sea water uses have considerable
promise. Desalination to potable level was accomplished. Ice growth
rates were obtained which indicate that ice structures of substantial size can
be built.This project was accomplished under a matching grant between the Office of
Water Resources Research, Department of the Interior, and the University
of Alaska, Arctic Environmental Engineering Laboratory. Funds available
under this grant purposefully did not anticipate the heavy logistic expense
in moving the project and equipment from Fairbanks to Kotzebue, Alaska.
Therefore, a major third contributor was the Alaska Air National Guard,
Kulis Air Force Base, Alaska. The support offered by the officers and men
of the Alaska Air National Guard was excellent and greatly appreciated
Nonequilibrium Dynamics of Charged Particles in an Electromagnetic Field: Causal and Stable Dynamics from 1/c Expansion of QED
We derive from a microscopic Hamiltonian a set of stochastic equations of
motion for a system of spinless charged particles in an electromagnetic (EM)
field based on a consistent application of a dimensionful 1/c expansion of
quantum electrodynamics (QED). All relativistic corrections up to order 1/c^3
are captured by the dynamics, which includes electrostatic interactions
(Coulomb), magnetostatic backreaction (Biot-Savart), dissipative backreaction
(Abraham-Lorentz) and quantum field fluctuations at zero and finite
temperatures. With self-consistent backreaction of the EM field included we
show that this approach yields causal and runaway-free equations of motion,
provides new insights into charged particle backreaction, and naturally leads
to equations consistent with the (classical) Darwin Hamiltonian and has quantum
operator ordering consistent with the Breit Hamiltonian. To order 1/c^3 the
approach leads to a nonstandard mass renormalization which is associated with
magnetostatic self-interactions, and no cutoff is required to prevent runaways.
Our new results also show that the pathologies of the standard Abraham-Lorentz
equations can be seen as a consequence of applying an inconsistent (i.e.
incomplete, mixed-order) expansion in 1/c, if, from the start, the analysis is
viewed as generating a low-energy effective theory rather than an exact
solution. Finally, we show that the 1/c expansion within a Hamiltonian
framework yields well-behaved noise and dissipation, in addition to the
multiple-particle interactions.Comment: 17 pages, 2 figure
A Framework to Manage the Complex Organisation of Collaborating: Its Application to Autonomous Systems
In this paper we present an analysis of the complexities of large group
collaboration and its application to develop detailed requirements for
collaboration schema for Autonomous Systems (AS). These requirements flow from
our development of a framework for collaboration that provides a basis for
designing, supporting and managing complex collaborative systems that can be
applied and tested in various real world settings. We present the concepts of
"collaborative flow" and "working as one" as descriptive expressions of what
good collaborative teamwork can be in such scenarios. The paper considers the
application of the framework within different scenarios and discuses the
utility of the framework in modelling and supporting collaboration in complex
organisational structures
Impaired Intracellular Transport and Cell Surface Expression of Nonpolymorphic HLA-E
The assembly of the classical, polymorphic major histocompatibility complex class I molecules
in the endoplasmic reticulum requires the presence of peptide ligands and ~2-microglobulin
(~2m). Formation of this trimolecular complex is a prerequisite for e~cient transport to the
cell surface, where presented peptides are scanned by T lymphocytes. The function of the other
class I molecules is in dispute. The human, nonclassical class I gene, HLA-E, was found to be
ubiquitously transcribed, whereas cell surface expression was dif~cult to detect upon transfection.
Pulse chase experiments revealed that the HLA-E heavy chain in transfectants, obtained with
the murine myeloma cell line P3X63-Ag8.653 (X63), displays a significant reduction in
oligosaccharide maturation and intracellular transport compared with HLA-B27 in corresponding
transfectants. The accordingly low HLA-E cell surface expression could be significantly enhanced
by either reducing the culture temperature or by supplementing the medium with human ~2m,
suggesting inefficient binding of endogenous peptides to HLA-E. To analyze whether HLA-E
binds peptides and to identify the corresponding ligands, fractions of acid-extracted material from
HLA-E/X63 transfectants were separated by reverse phase HPLC and were tested for their ability
to enhance HLA-E cell surface expression. Two fractions specifically increased the HLA class
I expression on the HLA-E transfectant clone
Mechanisms of direct reactions with halo nuclei
Halo nuclei are exotic nuclei which exhibit a strongly clusterised structure:
they can be seen as one or two valence nucleons loosely bound to a core. Being
observed at the ridge of the valley of stability, halo nuclei are studied
mostly through reactions. In this contribution the reaction models most
commonly used to analyse experimental data are reviewed and compared to one
another. A reaction observable built on the ratio of two angular distributions
is then presented. This ratio enables removing most of the sensitivity to the
reaction mechanism, which emphasises the effects of nuclear structure on the
reaction.Comment: Invited talk given by Pierre Capel at the "10th International
Conference on Clustering Aspects of Nuclear Structure and Dynamics"
(Cluster12), Debrecen, Hungary, 24-28 September 2012. To appear in the
Cluster12 Proceedings in the Open Access Journal of Physics: Conference
Series (JPCS). (5 pages, 3 figures
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