392 research outputs found
TIM, ray-tracing program for forbidden optics
TIM (The Interactive METATOY) is a ray-tracing program specifically tailored
towards our research in METATOYs, which are optical components that appear to
be able to create wave-optically forbidden light-ray fields. For this reason,
TIM possesses features not found in other ray-tracing programs. TIM can either
be used interactively or by modifying the openly available source code; in both
cases, it can easily be run as an applet embedded in a web page. Here we
describe the basic structure of TIM's source code and how to extend it, and we
give examples of how we have used TIM in our own research.Comment: 19 pages, 15 figure
Local light-ray rotation
We present a sheet structure that rotates the local ray direction through an
arbitrary angle around the sheet normal. The sheet structure consists of two
parallel Dove-prism sheets, each of which flips one component of the local
direction of transmitted light rays. Together, the two sheets rotate
transmitted light rays around the sheet normal. We show that the direction
under which a point light source is seen is given by a Mobius transform. We
illustrate some of the properties with movies calculated by ray-tracing
software.Comment: 9 pages, 6 figure
Design of a distributed hybrid electric propulsion system for a light aircraft based on genetic algorithm
Hybrid aircraft is a new attempt for next-generation aircraft, they are environmentally friendly and highly efficient. This paper proposes a new type of hybrid electric propulsion system for light aircraft, which integrated distributed propulsion concept and more electric aircraft concept together to improve aircraft performance. Based on the mission requirements and unique system configuration, all components, including engine, generator and motors are intelligently selected. The sizing problem can be divided into two parts. The power source part applied a non-dominated sorting genetic algorithm to choose components and simultaneously minimized total weight and fuel consumption. The rest of the system used a conventional genetic algorithm, which minimized weight and guaranteed that all selected motors can output enough power. In the end, by applying a simple deterministic energy management strategy, the new system achieved a 12% fuel consumption reduction
Parameter Diagrams of the GRW and CSL Theories of Wave Function Collapse
It has been hypothesized that the time evolution of wave functions might
include collapses, rather than being governed by the Schroedinger equation. The
leading models of such an evolution, GRW and CSL, both have two parameters (or
new constants of nature), the collapse width sigma and the collapse rate
lambda. We draw a diagram of the sigma-lambda-plane showing the region that is
empirically refuted and the region that is philosophically unsatisfactory.Comment: 17 pages LaTeX, 7 figure
Holography, Pade Approximants and Deconstruction
We investigate the relation between holographic calculations in 5D and the
Migdal approach to correlation functions in large N theories. The latter
employs Pade approximation to extrapolate short distance correlation functions
to large distances. We make the Migdal/5D relation more precise by quantifying
the correspondence between Pade approximation and the background and boundary
conditions in 5D. We also establish a connection between the Migdal approach
and the models of deconstructed dimensions.Comment: 28 page
NASA's Understanding of Risk in Apollo and Shuttle
Mathematical risk analysis was used in Apollo, but it gave unacceptably pessimistic resultsand was discontinued. Shuttle was designed without using risk analysis, under the assumptionthat good engineering would make it very safe. This approach led to an unnecessarily riskydesign, which directly led to the Shuttle tragedies. Although the Challenger disaster wasdirectly due to a mistaken launch decision, it might have been avoided by a safer design. Theultimate cause of the Shuttle tragedies was the Apollo era decision to abandon risk analysis
Infinitely many conservation laws for the discrete KdV equation
In \cite{RH3} Rasin and Hydon suggested a way to construct an infinite number
of conservation laws for the discrete KdV equation (dKdV), by repeated
application of a certain symmetry to a known conservation law. It was not
decided, however, whether the resulting conservation laws were distinct and
nontrivial. In this paper we obtain the following results: (1) We give an
alternative method to construct an infinite number of conservation laws using a
discrete version of the Gardner transformation. (2) We give a direct proof that
the Rasin-Hydon conservation laws are indeed distinct and nontrivial. (3) We
consider a continuum limit in which the dKdV equation becomes a first-order
eikonal equation. In this limit the two sets of conservation laws become the
same, and are evidently distinct and nontrivial. This proves the nontriviality
of the conservation laws constructed by the Gardner method, and gives an
alternate proof of the nontriviality of the conservation laws constructed by
the Rasin-Hydon method
A new model for health care delivery
<p>Abstract</p> <p>Background</p> <p>The health care delivery system in the United States is facing cost and quality pressures that will require fundamental changes to remain viable. The optimal structures of the relationships between the hospital, medical school, and physicians have not been determined but are likely to have a large impact on the future of healthcare delivery. Because it is generally agreed that academic medical centers will play a role in the sustainability of this future system, a fundamental understanding of the relative contributions of the stakeholders is important as well as creativity in developing novel strategies to achieve a shared vision.</p> <p>Discussion</p> <p>Core competencies of each of the stakeholders (the hospital, the medical school and the physicians) must complement the others and should act synergistically. At the same time, the stakeholders should determine the common core values and should be able to make a meaningful contribution to the delivery of health care.</p> <p>Summary</p> <p>Health care needs to achieve higher quality and lower cost. Therefore, in order for physicians, medical schools, and hospitals to serve the needs of society in a gratifying way, there will need to be change. There needs to be more scientific and social advances. It is obvious that there is a real and urgent need for relationship building among the professionals whose duty it is to provide these services.</p
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